/*
 License: http://www.apache.org/licenses/LICENSE-2.0 
 Home page: http://code.google.com/p/dapper-dot-net/

 Note: to build on C# 3.0 + .NET 3.5, include the CSHARP30 compiler symbol (and yes,
 I know the difference between language and runtime versions; this is a compromise).
 */

#if DNXCORE50
using IDbDataParameter = global::System.Data.Common.DbParameter;
using IDataParameter = global::System.Data.Common.DbParameter;
using IDbTransaction = global::System.Data.Common.DbTransaction;
using IDbConnection = global::System.Data.Common.DbConnection;
using IDbCommand = global::System.Data.Common.DbCommand;
using IDataReader = global::System.Data.Common.DbDataReader;
using IDataRecord = global::System.Data.Common.DbDataReader;
using IDataParameterCollection = global::System.Data.Common.DbParameterCollection;
using DataException = global::System.InvalidOperationException;
using ApplicationException = global::System.InvalidOperationException;
#endif

using System;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Linq;
using System.Reflection;
using System.Reflection.Emit;
using System.Text;
using System.Threading;
using System.Text.RegularExpressions;
using System.Diagnostics;
using System.Globalization;
using System.Linq.Expressions;
using System.Data.Common;

namespace Dapper
{
    [AssemblyNeutral, AttributeUsage(AttributeTargets.Class | AttributeTargets.Interface | AttributeTargets.Struct, AllowMultiple = false, Inherited = false)]
    internal sealed class AssemblyNeutralAttribute : Attribute { }

    /// <summary>
    /// Additional state flags that control command behaviour
    /// </summary>
    [Flags]
    public enum CommandFlags
    {
        /// <summary>
        /// No additional flags
        /// </summary>
        None = 0,
        /// <summary>
        /// Should data be buffered before returning?
        /// </summary>
        Buffered = 1,
        /// <summary>
        /// Can async queries be pipelined?
        /// </summary>
        Pipelined = 2,
        /// <summary>
        /// Should the plan cache be bypassed?
        /// </summary>
        NoCache = 4,
    }
    /// <summary>
    /// Represents the key aspects of a sql operation
    /// </summary>
    public struct CommandDefinition
    {
        internal static CommandDefinition ForCallback(object parameters)
        {
            if(parameters is DynamicParameters)
            {
                return new CommandDefinition(parameters);
            }
            else
            {
                return default(CommandDefinition);
            }
        }
        private readonly string commandText;
        private readonly object parameters;
        private readonly IDbTransaction transaction;
        private readonly int? commandTimeout;
        private readonly CommandType? commandType;
        private readonly CommandFlags flags;


        internal void OnCompleted()
        {
            if (parameters is SqlMapper.IParameterCallbacks)
            {
                ((SqlMapper.IParameterCallbacks)parameters).OnCompleted();
            }
        }
        /// <summary>
        /// The command (sql or a stored-procedure name) to execute
        /// </summary>
        public string CommandText { get { return commandText; } }
        /// <summary>
        /// The parameters associated with the command
        /// </summary>
        public object Parameters { get { return parameters; } }
        /// <summary>
        /// The active transaction for the command
        /// </summary>
        public IDbTransaction Transaction { get { return transaction; } }
        /// <summary>
        /// The effective timeout for the command
        /// </summary>
        public int? CommandTimeout { get { return commandTimeout; } }
        /// <summary>
        /// The type of command that the command-text represents
        /// </summary>
        public CommandType? CommandType { get { return commandType; } }

        /// <summary>
        /// Should data be buffered before returning?
        /// </summary>
        public bool Buffered { get { return (flags & CommandFlags.Buffered) != 0; } }

        /// <summary>
        /// Should the plan for this query be cached?
        /// </summary>
        internal bool AddToCache {  get { return (flags & CommandFlags.NoCache) == 0; } }

        /// <summary>
        /// Additional state flags against this command
        /// </summary>
        public CommandFlags Flags {  get { return flags; } }

        /// <summary>
        /// Can async queries be pipelined?
        /// </summary>
        public bool Pipelined { get { return (flags & CommandFlags.Pipelined) != 0; } }

        /// <summary>
        /// Initialize the command definition
        /// </summary>
#if CSHARP30
        public CommandDefinition(string commandText, object parameters, IDbTransaction transaction, int? commandTimeout,
            CommandType? commandType, CommandFlags flags)
#else
        public CommandDefinition(string commandText, object parameters = null, IDbTransaction transaction = null, int? commandTimeout = null,
            CommandType? commandType = null, CommandFlags flags = CommandFlags.Buffered
#if ASYNC
            , CancellationToken cancellationToken = default(CancellationToken)
#endif
            )
#endif
        {
            this.commandText = commandText;
            this.parameters = parameters;
            this.transaction = transaction;
            this.commandTimeout = commandTimeout;
            this.commandType = commandType;
            this.flags = flags;
#if ASYNC
            this.cancellationToken = cancellationToken;
#endif
        }

        private CommandDefinition(object parameters) : this()
        {
            this.parameters = parameters;
        }

#if ASYNC
        private readonly CancellationToken cancellationToken;
        /// <summary>
        /// For asynchronous operations, the cancellation-token
        /// </summary>
        public CancellationToken CancellationToken { get { return cancellationToken; } }
#endif

        internal IDbCommand SetupCommand(IDbConnection cnn, Action<IDbCommand, object> paramReader)
        {
            var cmd = cnn.CreateCommand();
            var init = GetInit(cmd.GetType());
            if (init != null) init(cmd);
            if (transaction != null)
                cmd.Transaction = transaction;
            cmd.CommandText = commandText;
            if (commandTimeout.HasValue)
                cmd.CommandTimeout = commandTimeout.Value;
            if (commandType.HasValue)
                cmd.CommandType = commandType.Value;
            if (paramReader != null)
            {
                paramReader(cmd, parameters);
            }
            return cmd;
        }

        static SqlMapper.Link<Type, Action<IDbCommand>> commandInitCache;
        static Action<IDbCommand> GetInit(Type commandType)
        {
            if (commandType == null) return null; // GIGO
            Action<IDbCommand> action;
            if (SqlMapper.Link<Type, Action<IDbCommand>>.TryGet(commandInitCache, commandType, out action))
            {
                return action;
            }
            var bindByName = GetBasicPropertySetter(commandType, "BindByName", typeof(bool));
            var initialLongFetchSize = GetBasicPropertySetter(commandType, "InitialLONGFetchSize", typeof(int));

            action = null;
            if (bindByName != null || initialLongFetchSize != null)
            {
                var method = new DynamicMethod(commandType.Name + "_init", null, new Type[] { typeof(IDbCommand) });
                var il = method.GetILGenerator();

                if (bindByName != null)
                {
                    // .BindByName = true
                    il.Emit(OpCodes.Ldarg_0);
                    il.Emit(OpCodes.Castclass, commandType);
                    il.Emit(OpCodes.Ldc_I4_1);
                    il.EmitCall(OpCodes.Callvirt, bindByName, null);
                }
                if (initialLongFetchSize != null)
                {
                    // .InitialLONGFetchSize = -1
                    il.Emit(OpCodes.Ldarg_0);
                    il.Emit(OpCodes.Castclass, commandType);
                    il.Emit(OpCodes.Ldc_I4_M1);
                    il.EmitCall(OpCodes.Callvirt, initialLongFetchSize, null);
                }
                il.Emit(OpCodes.Ret);
                action = (Action<IDbCommand>)method.CreateDelegate(typeof(Action<IDbCommand>));
            }
            // cache it            
            SqlMapper.Link<Type, Action<IDbCommand>>.TryAdd(ref commandInitCache, commandType, ref action);
            return action;
        }
        static MethodInfo GetBasicPropertySetter(Type declaringType, string name, Type expectedType)
        {
            var prop = declaringType.GetProperty(name, BindingFlags.Public | BindingFlags.Instance);
            ParameterInfo[] indexers;
            if (prop != null && prop.CanWrite && prop.PropertyType == expectedType
                && ((indexers = prop.GetIndexParameters()) == null || indexers.Length == 0))
            {
                return prop.GetSetMethod();
            }
            return null;
        }
    }

    /// <summary>
    /// Dapper, a light weight object mapper for ADO.NET
    /// </summary>
    static partial class SqlMapper
    {
        /// <summary>
        /// Implement this interface to pass an arbitrary db specific set of parameters to Dapper
        /// </summary>
        public partial interface IDynamicParameters
        {
            /// <summary>
            /// Add all the parameters needed to the command just before it executes
            /// </summary>
            /// <param name="command">The raw command prior to execution</param>
            /// <param name="identity">Information about the query</param>
            void AddParameters(IDbCommand command, Identity identity);
        }

        /// <summary>
        /// Extends IDynamicParameters providing by-name lookup of parameter values
        /// </summary>
        public interface IParameterLookup : IDynamicParameters
        {
            /// <summary>
            /// Get the value of the specified parameter (return null if not found)
            /// </summary>
            object this[string name] { get; }
        }

        /// <summary>
        /// Extends IDynamicParameters with facilities for executing callbacks after commands have completed
        /// </summary>
        public partial interface IParameterCallbacks : IDynamicParameters
        {
            /// <summary>
            /// Invoked when the command has executed
            /// </summary>
            void OnCompleted();
        }

        /// <summary>
        /// Implement this interface to pass an arbitrary db specific parameter to Dapper
        /// </summary>
        [AssemblyNeutral]
        public interface ICustomQueryParameter
        {
            /// <summary>
            /// Add the parameter needed to the command before it executes
            /// </summary>
            /// <param name="command">The raw command prior to execution</param>
            /// <param name="name">Parameter name</param>
            void AddParameter(IDbCommand command, string name);
        }

        /// <summary>
        /// Implement this interface to perform custom type-based parameter handling and value parsing
        /// </summary>
        [AssemblyNeutral]
        public interface ITypeHandler
        {
            /// <summary>
            /// Assign the value of a parameter before a command executes
            /// </summary>
            /// <param name="parameter">The parameter to configure</param>
            /// <param name="value">Parameter value</param>
            void SetValue(IDbDataParameter parameter, object value);

            /// <summary>
            /// Parse a database value back to a typed value
            /// </summary>
            /// <param name="value">The value from the database</param>
            /// <param name="destinationType">The type to parse to</param>
            /// <returns>The typed value</returns>
            object Parse(Type destinationType, object value);
        }
#if !DNXCORE50
        /// <summary>
        /// A type handler for data-types that are supported by the underlying provider, but which need
        /// a well-known UdtTypeName to be specified
        /// </summary>
        public class UdtTypeHandler : ITypeHandler
        {
            private readonly string udtTypeName;
            /// <summary>
            /// Creates a new instance of UdtTypeHandler with the specified UdtTypeName
            /// </summary>
            public UdtTypeHandler(string udtTypeName)
            {
                if (string.IsNullOrEmpty(udtTypeName)) throw new ArgumentException("Cannot be null or empty", udtTypeName);
                this.udtTypeName = udtTypeName;
            }
            object ITypeHandler.Parse(Type destinationType, object value)
            {
                return value is DBNull ? null : value;
            }

            void ITypeHandler.SetValue(IDbDataParameter parameter, object value)
            {
                parameter.Value = SanitizeParameterValue(value);
                if (parameter is System.Data.SqlClient.SqlParameter)
                {
                    ((System.Data.SqlClient.SqlParameter)parameter).UdtTypeName = udtTypeName;
                }
            }
        }
#endif

        /// <summary>
        /// Base-class for simple type-handlers
        /// </summary>
        public abstract class TypeHandler<T> : ITypeHandler
        {
            /// <summary>
            /// Assign the value of a parameter before a command executes
            /// </summary>
            /// <param name="parameter">The parameter to configure</param>
            /// <param name="value">Parameter value</param>
            public abstract void SetValue(IDbDataParameter parameter, T value);

            /// <summary>
            /// Parse a database value back to a typed value
            /// </summary>
            /// <param name="value">The value from the database</param>
            /// <returns>The typed value</returns>
            public abstract T Parse(object value);

            void ITypeHandler.SetValue(IDbDataParameter parameter, object value)
            {
                if (value is DBNull)
                {
                    parameter.Value = value;
                }
                else
                {
                    SetValue(parameter, (T)value);
                }
            }

            object ITypeHandler.Parse(Type destinationType, object value)
            {
                return Parse(value);
            }
        }

        /// <summary>
        /// Implement this interface to change default mapping of reader columns to type members
        /// </summary>
        public interface ITypeMap
        {
            /// <summary>
            /// Finds best constructor
            /// </summary>
            /// <param name="names">DataReader column names</param>
            /// <param name="types">DataReader column types</param>
            /// <returns>Matching constructor or default one</returns>
            ConstructorInfo FindConstructor(string[] names, Type[] types);

            /// <summary>
            /// Returns a constructor which should *always* be used.
            /// 
            /// Parameters will be default values, nulls for reference types and zero'd for value types.
            /// 
            /// Use this class to force object creation away from parameterless constructors you don't control.
            /// </summary>
            ConstructorInfo FindExplicitConstructor();

            /// <summary>
            /// Gets mapping for constructor parameter
            /// </summary>
            /// <param name="constructor">Constructor to resolve</param>
            /// <param name="columnName">DataReader column name</param>
            /// <returns>Mapping implementation</returns>
            IMemberMap GetConstructorParameter(ConstructorInfo constructor, string columnName);

            /// <summary>
            /// Gets member mapping for column
            /// </summary>
            /// <param name="columnName">DataReader column name</param>
            /// <returns>Mapping implementation</returns>
            IMemberMap GetMember(string columnName);
        }

        /// <summary>
        /// Implements this interface to provide custom member mapping
        /// </summary>
        public interface IMemberMap
        {
            /// <summary>
            /// Source DataReader column name
            /// </summary>
            string ColumnName { get; }

            /// <summary>
            ///  Target member type
            /// </summary>
            Type MemberType { get; }

            /// <summary>
            /// Target property
            /// </summary>
            PropertyInfo Property { get; }

            /// <summary>
            /// Target field
            /// </summary>
            FieldInfo Field { get; }

            /// <summary>
            /// Target constructor parameter
            /// </summary>
            ParameterInfo Parameter { get; }
        }

        /// <summary>
        /// This is a micro-cache; suitable when the number of terms is controllable (a few hundred, for example),
        /// and strictly append-only; you cannot change existing values. All key matches are on **REFERENCE**
        /// equality. The type is fully thread-safe.
        /// </summary>
        internal partial class Link<TKey, TValue> where TKey : class
        {
            public static bool TryGet(Link<TKey, TValue> link, TKey key, out TValue value)
            {
                while (link != null)
                {
                    if ((object)key == (object)link.Key)
                    {
                        value = link.Value;
                        return true;
                    }
                    link = link.Tail;
                }
                value = default(TValue);
                return false;
            }
            public static bool TryAdd(ref Link<TKey, TValue> head, TKey key, ref TValue value)
            {
                bool tryAgain;
                do
                {
                    var snapshot = Interlocked.CompareExchange(ref head, null, null);
                    TValue found;
                    if (TryGet(snapshot, key, out found))
                    { // existing match; report the existing value instead
                        value = found;
                        return false;
                    }
                    var newNode = new Link<TKey, TValue>(key, value, snapshot);
                    // did somebody move our cheese?
                    tryAgain = Interlocked.CompareExchange(ref head, newNode, snapshot) != snapshot;
                } while (tryAgain);
                return true;
            }
            private Link(TKey key, TValue value, Link<TKey, TValue> tail)
            {
                Key = key;
                Value = value;
                Tail = tail;
            }
            public TKey Key { get; private set; }
            public TValue Value { get; private set; }
            public Link<TKey, TValue> Tail { get; private set; }
        }
        partial class CacheInfo
        {
            public DeserializerState Deserializer { get; set; }
            public Func<IDataReader, object>[] OtherDeserializers { get; set; }
            public Action<IDbCommand, object> ParamReader { get; set; }
            private int hitCount;
            public int GetHitCount() { return Interlocked.CompareExchange(ref hitCount, 0, 0); }
            public void RecordHit() { Interlocked.Increment(ref hitCount); }
        }
        static int GetColumnHash(IDataReader reader)
        {
            unchecked
            {
                int colCount = reader.FieldCount, hash = colCount;
                for (int i = 0; i < colCount; i++)
                {   // binding code is only interested in names - not types
                    object tmp = reader.GetName(i);
                    hash = (hash * 31) + (tmp == null ? 0 : tmp.GetHashCode());
                }
                return hash;
            }
        }
        struct DeserializerState
        {
            public readonly int Hash;
            public readonly Func<IDataReader, object> Func;

            public DeserializerState(int hash, Func<IDataReader, object> func)
            {
                Hash = hash;
                Func = func;
            }
        }

        /// <summary>
        /// Called if the query cache is purged via PurgeQueryCache
        /// </summary>
        public static event EventHandler QueryCachePurged;
        private static void OnQueryCachePurged()
        {
            var handler = QueryCachePurged;
            if (handler != null) handler(null, EventArgs.Empty);
        }
#if CSHARP30
        private static readonly Dictionary<Identity, CacheInfo> _queryCache = new Dictionary<Identity, CacheInfo>();
        // note: conflicts between readers and writers are so short-lived that it isn't worth the overhead of
        // ReaderWriterLockSlim etc; a simple lock is faster
        private static void SetQueryCache(Identity key, CacheInfo value)
        {
            lock (_queryCache) { _queryCache[key] = value; }
        }
        private static bool TryGetQueryCache(Identity key, out CacheInfo value)
        {
            lock (_queryCache) { return _queryCache.TryGetValue(key, out value); }
        }
        private static void PurgeQueryCacheByType(Type type)
        {
            lock (_queryCache)
            {
                var toRemove = _queryCache.Keys.Where(id => id.type == type).ToArray();
                foreach (var key in toRemove)
                    _queryCache.Remove(key);
            }
        }
        /// <summary>
        /// Purge the query cache 
        /// </summary>
        public static void PurgeQueryCache()
        {
            lock (_queryCache)
            {
                _queryCache.Clear();
            }
            OnQueryCachePurged();
        }
#else
        static readonly System.Collections.Concurrent.ConcurrentDictionary<Identity, CacheInfo> _queryCache = new System.Collections.Concurrent.ConcurrentDictionary<Identity, CacheInfo>();
        private static void SetQueryCache(Identity key, CacheInfo value)
        {
            if (Interlocked.Increment(ref collect) == COLLECT_PER_ITEMS)
            {
                CollectCacheGarbage();
            }
            _queryCache[key] = value;
        }

        private static void CollectCacheGarbage()
        {
            try
            {
                foreach (var pair in _queryCache)
                {
                    if (pair.Value.GetHitCount() <= COLLECT_HIT_COUNT_MIN)
                    {
                        CacheInfo cache;
                        _queryCache.TryRemove(pair.Key, out cache);
                    }
                }
            }

            finally
            {
                Interlocked.Exchange(ref collect, 0);
            }
        }

        private const int COLLECT_PER_ITEMS = 1000, COLLECT_HIT_COUNT_MIN = 0;
        private static int collect;
        private static bool TryGetQueryCache(Identity key, out CacheInfo value)
        {
            if (_queryCache.TryGetValue(key, out value))
            {
                value.RecordHit();
                return true;
            }
            value = null;
            return false;
        }

        /// <summary>
        /// Purge the query cache 
        /// </summary>
        public static void PurgeQueryCache()
        {
            _queryCache.Clear();
            OnQueryCachePurged();
        }

        private static void PurgeQueryCacheByType(Type type)
        {
            foreach (var entry in _queryCache)
            {
                CacheInfo cache;
                if (entry.Key.type == type)
                    _queryCache.TryRemove(entry.Key, out cache);
            }
        }

        /// <summary>
        /// Return a count of all the cached queries by dapper
        /// </summary>
        /// <returns></returns>
        public static int GetCachedSQLCount()
        {
            return _queryCache.Count;
        }

        /// <summary>
        /// Return a list of all the queries cached by dapper
        /// </summary>
        /// <param name="ignoreHitCountAbove"></param>
        /// <returns></returns>
        public static IEnumerable<Tuple<string, string, int>> GetCachedSQL(int ignoreHitCountAbove = int.MaxValue)
        {
            var data = _queryCache.Select(pair => Tuple.Create(pair.Key.connectionString, pair.Key.sql, pair.Value.GetHitCount()));
            if (ignoreHitCountAbove < int.MaxValue) data = data.Where(tuple => tuple.Item3 <= ignoreHitCountAbove);
            return data;
        }

        /// <summary>
        /// Deep diagnostics only: find any hash collisions in the cache
        /// </summary>
        /// <returns></returns>
        public static IEnumerable<Tuple<int, int>> GetHashCollissions()
        {
            var counts = new Dictionary<int, int>();
            foreach (var key in _queryCache.Keys)
            {
                int count;
                if (!counts.TryGetValue(key.hashCode, out count))
                {
                    counts.Add(key.hashCode, 1);
                }
                else
                {
                    counts[key.hashCode] = count + 1;
                }
            }
            return from pair in counts
                   where pair.Value > 1
                   select Tuple.Create(pair.Key, pair.Value);

        }
#endif


        static Dictionary<Type, DbType> typeMap;

        static SqlMapper()
        {
            typeMap = new Dictionary<Type, DbType>();
            typeMap[typeof(byte)] = DbType.Byte;
            typeMap[typeof(sbyte)] = DbType.SByte;
            typeMap[typeof(short)] = DbType.Int16;
            typeMap[typeof(ushort)] = DbType.UInt16;
            typeMap[typeof(int)] = DbType.Int32;
            typeMap[typeof(uint)] = DbType.UInt32;
            typeMap[typeof(long)] = DbType.Int64;
            typeMap[typeof(ulong)] = DbType.UInt64;
            typeMap[typeof(float)] = DbType.Single;
            typeMap[typeof(double)] = DbType.Double;
            typeMap[typeof(decimal)] = DbType.Decimal;
            typeMap[typeof(bool)] = DbType.Boolean;
            typeMap[typeof(string)] = DbType.String;
            typeMap[typeof(char)] = DbType.StringFixedLength;
            typeMap[typeof(Guid)] = DbType.Guid;
            typeMap[typeof(DateTime)] = DbType.DateTime;
            typeMap[typeof(DateTimeOffset)] = DbType.DateTimeOffset;
            typeMap[typeof(TimeSpan)] = DbType.Time;
            typeMap[typeof(byte[])] = DbType.Binary;
            typeMap[typeof(byte?)] = DbType.Byte;
            typeMap[typeof(sbyte?)] = DbType.SByte;
            typeMap[typeof(short?)] = DbType.Int16;
            typeMap[typeof(ushort?)] = DbType.UInt16;
            typeMap[typeof(int?)] = DbType.Int32;
            typeMap[typeof(uint?)] = DbType.UInt32;
            typeMap[typeof(long?)] = DbType.Int64;
            typeMap[typeof(ulong?)] = DbType.UInt64;
            typeMap[typeof(float?)] = DbType.Single;
            typeMap[typeof(double?)] = DbType.Double;
            typeMap[typeof(decimal?)] = DbType.Decimal;
            typeMap[typeof(bool?)] = DbType.Boolean;
            typeMap[typeof(char?)] = DbType.StringFixedLength;
            typeMap[typeof(Guid?)] = DbType.Guid;
            typeMap[typeof(DateTime?)] = DbType.DateTime;
            typeMap[typeof(DateTimeOffset?)] = DbType.DateTimeOffset;
            typeMap[typeof(TimeSpan?)] = DbType.Time;
            typeMap[typeof(object)] = DbType.Object;
#if !DNXCORE50
            AddTypeHandlerImpl(typeof(DataTable), new DataTableHandler(), false);
#endif
        }

        /// <summary>
        /// Clear the registered type handlers
        /// </summary>
        public static void ResetTypeHandlers()
        {
            typeHandlers = new Dictionary<Type, ITypeHandler>();
#if !DNXCORE50
            AddTypeHandlerImpl(typeof(DataTable), new DataTableHandler(), true);
#endif
        }
        /// <summary>
        /// Configure the specified type to be mapped to a given db-type
        /// </summary>
        public static void AddTypeMap(Type type, DbType dbType)
        {
            // use clone, mutate, replace to avoid threading issues
            var snapshot = typeMap;

            DbType oldValue;
            if (snapshot.TryGetValue(type, out oldValue) && oldValue == dbType) return; // nothing to do

            var newCopy = new Dictionary<Type, DbType>(snapshot);
            newCopy[type] = dbType;
            typeMap = newCopy;
        }

        /// <summary>
        /// Configure the specified type to be processed by a custom handler
        /// </summary>
        public static void AddTypeHandler(Type type, ITypeHandler handler)
        {
            AddTypeHandlerImpl(type, handler, true);
        }

        /// <summary>
        /// Configure the specified type to be processed by a custom handler
        /// </summary>
        public static void AddTypeHandlerImpl(Type type, ITypeHandler handler, bool clone)
        {
            if (type == null) throw new ArgumentNullException("type");

            Type secondary = null;
            if(type.IsValueType())
            {
                var underlying = Nullable.GetUnderlyingType(type);
                if(underlying == null)
                {
                    secondary = typeof(Nullable<>).MakeGenericType(type); // the Nullable<T>
                    // type is already the T
                }
                else
                {
                    secondary = type; // the Nullable<T>
                    type = underlying; // the T
                }
            }

            var snapshot = typeHandlers;
            ITypeHandler oldValue;
            if (snapshot.TryGetValue(type, out oldValue) && handler == oldValue) return; // nothing to do

            var newCopy = clone ? new Dictionary<Type, ITypeHandler>(snapshot) : snapshot;

#pragma warning disable 618
            typeof(TypeHandlerCache<>).MakeGenericType(type).GetMethod("SetHandler", BindingFlags.Static | BindingFlags.NonPublic).Invoke(null, new object[] { handler });
            if(secondary != null)
            {
                typeof(TypeHandlerCache<>).MakeGenericType(secondary).GetMethod("SetHandler", BindingFlags.Static | BindingFlags.NonPublic).Invoke(null, new object[] { handler });
            }
#pragma warning restore 618
            if (handler == null)
            {
                newCopy.Remove(type);
                if (secondary != null) newCopy.Remove(secondary);
            }
            else
            {
                newCopy[type] = handler;
                if(secondary != null) newCopy[secondary] = handler;
            }
            typeHandlers = newCopy;
        }

        /// <summary>
        /// Configure the specified type to be processed by a custom handler
        /// </summary>
        public static void AddTypeHandler<T>(TypeHandler<T> handler)
        {
            AddTypeHandlerImpl(typeof(T), handler, true);
        }

        /// <summary>
        /// Not intended for direct usage
        /// </summary>
        [Obsolete("Not intended for direct usage", false)]
#if !DNXCORE50
        [Browsable(false)]
#endif
        [EditorBrowsable(EditorBrowsableState.Never)]
        public static class TypeHandlerCache<T>
        {
            /// <summary>
            /// Not intended for direct usage
            /// </summary>
            [Obsolete("Not intended for direct usage", true)]
            public static T Parse(object value)
            {
                return (T)handler.Parse(typeof(T), value);
                
            }

            /// <summary>
            /// Not intended for direct usage
            /// </summary>
            [Obsolete("Not intended for direct usage", true)]
            public static void SetValue(IDbDataParameter parameter, object value)
            {
                handler.SetValue(parameter, value);
            }

            internal static void SetHandler(ITypeHandler handler)
            {
#pragma warning disable 618
                TypeHandlerCache<T>.handler = handler;
#pragma warning restore 618
            }

            private static ITypeHandler handler;
        }

        private static Dictionary<Type, ITypeHandler> typeHandlers = new Dictionary<Type, ITypeHandler>();

        internal const string LinqBinary = "System.Data.Linq.Binary";

        /// <summary>
        /// Get the DbType that maps to a given value
        /// </summary>
        [Obsolete("This method is for internal use only")]
#if !DNXCORE50
        [Browsable(false)]
#endif
        [EditorBrowsable(EditorBrowsableState.Never)]
        public static DbType GetDbType(object value)
        {
            if (value == null || value is DBNull) return DbType.Object;

            ITypeHandler handler;
            return LookupDbType(value.GetType(), "n/a", false, out handler);

        }
        internal static DbType LookupDbType(Type type, string name, bool demand, out ITypeHandler handler)
        {
            DbType dbType;
            handler = null;
            var nullUnderlyingType = Nullable.GetUnderlyingType(type);
            if (nullUnderlyingType != null) type = nullUnderlyingType;
            if (type.IsEnum() && !typeMap.ContainsKey(type))
            {
                type = Enum.GetUnderlyingType(type);
            }
            if (typeMap.TryGetValue(type, out dbType))
            {
                return dbType;
            }
            if (type.FullName == LinqBinary)
            {
                return DbType.Binary;
            }
            if (typeof(IEnumerable).IsAssignableFrom(type))
            {
                return DynamicParameters.EnumerableMultiParameter;
            }

            if (typeHandlers.TryGetValue(type, out handler))
            {
                return DbType.Object;
            }
#if !DNXCORE50
            switch (type.FullName)
            {
                case "Microsoft.SqlServer.Types.SqlGeography":
                    AddTypeHandler(type, handler = new UdtTypeHandler("geography"));
                    return DbType.Object;
                case "Microsoft.SqlServer.Types.SqlGeometry":
                    AddTypeHandler(type, handler = new UdtTypeHandler("geometry"));
                    return DbType.Object;
                case "Microsoft.SqlServer.Types.SqlHierarchyId":
                    AddTypeHandler(type, handler = new UdtTypeHandler("hierarchyid"));
                    return DbType.Object;
            }
#endif
            if(demand)
                throw new NotSupportedException(string.Format("The member {0} of type {1} cannot be used as a parameter value", name, type.FullName));
            return DbType.Object;

        }

        /// <summary>
        /// Identity of a cached query in Dapper, used for extensibility
        /// </summary>
        public partial class Identity : IEquatable<Identity>
        {
            internal Identity ForGrid(Type primaryType, int gridIndex)
            {
                return new Identity(sql, commandType, connectionString, primaryType, parametersType, null, gridIndex);
            }

            internal Identity ForGrid(Type primaryType, Type[] otherTypes, int gridIndex)
            {
                return new Identity(sql, commandType, connectionString, primaryType, parametersType, otherTypes, gridIndex);
            }
            /// <summary>
            /// Create an identity for use with DynamicParameters, internal use only
            /// </summary>
            /// <param name="type"></param>
            /// <returns></returns>
            public Identity ForDynamicParameters(Type type)
            {
                return new Identity(sql, commandType, connectionString, this.type, type, null, -1);
            }

            internal Identity(string sql, CommandType? commandType, IDbConnection connection, Type type, Type parametersType, Type[] otherTypes)
                : this(sql, commandType, connection.ConnectionString, type, parametersType, otherTypes, 0)
            { }
            private Identity(string sql, CommandType? commandType, string connectionString, Type type, Type parametersType, Type[] otherTypes, int gridIndex)
            {
                this.sql = sql;
                this.commandType = commandType;
                this.connectionString = connectionString;
                this.type = type;
                this.parametersType = parametersType;
                this.gridIndex = gridIndex;
                unchecked
                {
                    hashCode = 17; // we *know* we are using this in a dictionary, so pre-compute this
                    hashCode = hashCode * 23 + commandType.GetHashCode();
                    hashCode = hashCode * 23 + gridIndex.GetHashCode();
                    hashCode = hashCode * 23 + (sql == null ? 0 : sql.GetHashCode());
                    hashCode = hashCode * 23 + (type == null ? 0 : type.GetHashCode());
                    if (otherTypes != null)
                    {
                        foreach (var t in otherTypes)
                        {
                            hashCode = hashCode * 23 + (t == null ? 0 : t.GetHashCode());
                        }
                    }
                    hashCode = hashCode * 23 + (connectionString == null ? 0 : SqlMapper.connectionStringComparer.GetHashCode(connectionString));
                    hashCode = hashCode * 23 + (parametersType == null ? 0 : parametersType.GetHashCode());
                }
            }

            /// <summary>
            /// 
            /// </summary>
            /// <param name="obj"></param>
            /// <returns></returns>
            public override bool Equals(object obj)
            {
                return Equals(obj as Identity);
            }
            /// <summary>
            /// The sql
            /// </summary>
            public readonly string sql;
            /// <summary>
            /// The command type 
            /// </summary>
            public readonly CommandType? commandType;

            /// <summary>
            /// 
            /// </summary>
            public readonly int hashCode, gridIndex;
            /// <summary>
            /// 
            /// </summary>
            public readonly Type type;
            /// <summary>
            /// 
            /// </summary>
            public readonly string connectionString;
            /// <summary>
            /// 
            /// </summary>
            public readonly Type parametersType;
            /// <summary>
            /// 
            /// </summary>
            /// <returns></returns>
            public override int GetHashCode()
            {
                return hashCode;
            }
            /// <summary>
            /// Compare 2 Identity objects
            /// </summary>
            /// <param name="other"></param>
            /// <returns></returns>
            public bool Equals(Identity other)
            {
                return
                    other != null &&
                    gridIndex == other.gridIndex &&
                    type == other.type &&
                    sql == other.sql &&
                    commandType == other.commandType &&
                    SqlMapper.connectionStringComparer.Equals(connectionString, other.connectionString) &&
                    parametersType == other.parametersType;
            }
        }

        /// <summary>
        /// Obtains the data as a list; if it is *already* a list, the original object is returned without
        /// any duplication; otherwise, ToList() is invoked.
        /// </summary>
        public static List<T> AsList<T>(this IEnumerable<T> source)
        {
            return (source == null || source is List<T>) ? (List<T>)source : source.ToList();
        }

#if CSHARP30
        /// <summary>
        /// Execute parameterized SQL  
        /// </summary>
        /// <returns>Number of rows affected</returns>
        public static int Execute(this IDbConnection cnn, string sql, object param)
        {
            return Execute(cnn, sql, param, null, null, null);
        }

        /// <summary>
        /// Execute parameterized SQL
        /// </summary>
        /// <returns>Number of rows affected</returns>
        public static int Execute(this IDbConnection cnn, string sql, object param, IDbTransaction transaction)
        {
            return Execute(cnn, sql, param, transaction, null, null);
        }

        /// <summary>
        /// Execute parameterized SQL
        /// </summary>
        /// <returns>Number of rows affected</returns>
        public static int Execute(this IDbConnection cnn, string sql, object param, CommandType commandType)
        {
            return Execute(cnn, sql, param, null, null, commandType);
        }

        /// <summary>
        /// Execute parameterized SQL
        /// </summary>
        /// <returns>Number of rows affected</returns>
        public static int Execute(this IDbConnection cnn, string sql, object param, IDbTransaction transaction, CommandType commandType)
        {
            return Execute(cnn, sql, param, transaction, null, commandType);
        }

        /// <summary>
        /// Execute parameterized SQL and return an <see cref="IDataReader"/>
        /// </summary>
        /// <returns>An <see cref="IDataReader"/> that can be used to iterate over the results of the SQL query.</returns>
        public static IDataReader ExecuteReader(this IDbConnection cnn, string sql, object param)
        {
            return ExecuteReader(cnn, sql, param, null, null, null);
        }

        /// <summary>
        /// Execute parameterized SQL and return an <see cref="IDataReader"/>
        /// </summary>
        /// <returns>An <see cref="IDataReader"/> that can be used to iterate over the results of the SQL query.</returns>
        public static IDataReader ExecuteReader(this IDbConnection cnn, string sql, object param, IDbTransaction transaction)
        {
            return ExecuteReader(cnn, sql, param, transaction, null, null);
        }

        /// <summary>
        /// Execute parameterized SQL and return an <see cref="IDataReader"/>
        /// </summary>
        /// <returns>An <see cref="IDataReader"/> that can be used to iterate over the results of the SQL query.</returns>
        public static IDataReader ExecuteReader(this IDbConnection cnn, string sql, object param, CommandType commandType)
        {
            return ExecuteReader(cnn, sql, param, null, null, commandType);
        }

        /// <summary>
        /// Execute parameterized SQL and return an <see cref="IDataReader"/>
        /// </summary>
        /// <returns>An <see cref="IDataReader"/> that can be used to iterate over the results of the SQL query.</returns>
        public static IDataReader ExecuteReader(this IDbConnection cnn, string sql, object param, IDbTransaction transaction, CommandType commandType)
        {
            return ExecuteReader(cnn, sql, param, transaction, null, commandType);
        }

        /// <summary>
        /// Executes a query, returning the data typed as per T
        /// </summary>
        /// <returns>A sequence of data of the supplied type; if a basic type (int, string, etc) is queried then the data from the first column in assumed, otherwise an instance is
        /// created per row, and a direct column-name===member-name mapping is assumed (case insensitive).
        /// </returns>
        public static IEnumerable<T> Query<T>(this IDbConnection cnn, string sql, object param)
        {
            return Query<T>(cnn, sql, param, null, true, null, null);
        }

        /// <summary>
        /// Executes a query, returning the data typed as per T
        /// </summary>
        /// <returns>A sequence of data of the supplied type; if a basic type (int, string, etc) is queried then the data from the first column in assumed, otherwise an instance is
        /// created per row, and a direct column-name===member-name mapping is assumed (case insensitive).
        /// </returns>
        public static IEnumerable<T> Query<T>(this IDbConnection cnn, string sql, object param, IDbTransaction transaction)
        {
            return Query<T>(cnn, sql, param, transaction, true, null, null);
        }

        /// <summary>
        /// Executes a query, returning the data typed as per T
        /// </summary>
        /// <returns>A sequence of data of the supplied type; if a basic type (int, string, etc) is queried then the data from the first column in assumed, otherwise an instance is
        /// created per row, and a direct column-name===member-name mapping is assumed (case insensitive).
        /// </returns>
        public static IEnumerable<T> Query<T>(this IDbConnection cnn, string sql, object param, CommandType commandType)
        {
            return Query<T>(cnn, sql, param, null, true, null, commandType);
        }

        /// <summary>
        /// Executes a query, returning the data typed as per T
        /// </summary>
        /// <returns>A sequence of data of the supplied type; if a basic type (int, string, etc) is queried then the data from the first column in assumed, otherwise an instance is
        /// created per row, and a direct column-name===member-name mapping is assumed (case insensitive).
        /// </returns>
        public static IEnumerable<T> Query<T>(this IDbConnection cnn, string sql, object param, IDbTransaction transaction, CommandType commandType)
        {
            return Query<T>(cnn, sql, param, transaction, true, null, commandType);
        }

        /// <summary>
        /// Execute a command that returns multiple result sets, and access each in turn
        /// </summary>
        public static GridReader QueryMultiple(this IDbConnection cnn, string sql, object param, IDbTransaction transaction)
        {
            return QueryMultiple(cnn, sql, param, transaction, null, null);
        }

        /// <summary>
        /// Execute a command that returns multiple result sets, and access each in turn
        /// </summary>
        public static GridReader QueryMultiple(this IDbConnection cnn, string sql, object param, CommandType commandType)
        {
            return QueryMultiple(cnn, sql, param, null, null, commandType);
        }

        /// <summary>
        /// Execute a command that returns multiple result sets, and access each in turn
        /// </summary>
        public static GridReader QueryMultiple(this IDbConnection cnn, string sql, object param, IDbTransaction transaction, CommandType commandType)
        {
            return QueryMultiple(cnn, sql, param, transaction, null, commandType);
        }
#endif


        /// <summary>
        /// Execute parameterized SQL  
        /// </summary>
        /// <returns>Number of rows affected</returns>
        public static int Execute(
#if CSHARP30
this IDbConnection cnn, string sql, object param, IDbTransaction transaction, int? commandTimeout, CommandType? commandType
#else
this IDbConnection cnn, string sql, object param = null, IDbTransaction transaction = null, int? commandTimeout = null, CommandType? commandType = null
#endif
)
        {
            var command = new CommandDefinition(sql, (object)param, transaction, commandTimeout, commandType, CommandFlags.Buffered);
            return ExecuteImpl(cnn, ref command);
        }
        /// <summary>
        /// Execute parameterized SQL  
        /// </summary>
        /// <returns>Number of rows affected</returns>
        public static int Execute(this IDbConnection cnn, CommandDefinition command)
        {
            return ExecuteImpl(cnn, ref command);
        }


        /// <summary>
        /// Execute parameterized SQL that selects a single value
        /// </summary>
        /// <returns>The first cell selected</returns>
        public static object ExecuteScalar(
#if CSHARP30
this IDbConnection cnn, string sql, object param, IDbTransaction transaction, int? commandTimeout, CommandType? commandType
#else
this IDbConnection cnn, string sql, object param = null, IDbTransaction transaction = null, int? commandTimeout = null, CommandType? commandType = null
#endif
)
        {
            var command = new CommandDefinition(sql, (object)param, transaction, commandTimeout, commandType, CommandFlags.Buffered);
            return ExecuteScalarImpl<object>(cnn, ref command);
        }

        /// <summary>
        /// Execute parameterized SQL that selects a single value
        /// </summary>
        /// <returns>The first cell selected</returns>
        public static T ExecuteScalar<T>(
#if CSHARP30
this IDbConnection cnn, string sql, object param, IDbTransaction transaction, int? commandTimeout, CommandType? commandType
#else
this IDbConnection cnn, string sql, object param = null, IDbTransaction transaction = null, int? commandTimeout = null, CommandType? commandType = null
#endif
)
        {
            var command = new CommandDefinition(sql, (object)param, transaction, commandTimeout, commandType, CommandFlags.Buffered);
            return ExecuteScalarImpl<T>(cnn, ref command);
        }

        /// <summary>
        /// Execute parameterized SQL that selects a single value
        /// </summary>
        /// <returns>The first cell selected</returns>
        public static object ExecuteScalar(this IDbConnection cnn, CommandDefinition command)
        {
            return ExecuteScalarImpl<object>(cnn, ref command);
        }

        /// <summary>
        /// Execute parameterized SQL that selects a single value
        /// </summary>
        /// <returns>The first cell selected</returns>
        public static T ExecuteScalar<T>(this IDbConnection cnn, CommandDefinition command)
        {
            return ExecuteScalarImpl<T>(cnn, ref command);
        }

        private static IEnumerable GetMultiExec(object param)
        {
            return (param is IEnumerable
                && !(param is string || param is IEnumerable<KeyValuePair<string, object>>
                    )) ? (IEnumerable)param : null;
        }

        private static int ExecuteImpl(this IDbConnection cnn, ref CommandDefinition command)
        {
            object param = command.Parameters;
            IEnumerable multiExec = GetMultiExec(param);
            Identity identity;
            CacheInfo info = null;
            if (multiExec != null)
            {
#if ASYNC
                if((command.Flags & CommandFlags.Pipelined) != 0)
                {
                    // this includes all the code for concurrent/overlapped query
                    return ExecuteMultiImplAsync(cnn, command, multiExec).Result;
                }
#endif
                bool isFirst = true;
                int total = 0;
                bool wasClosed = cnn.State == ConnectionState.Closed;
                try
                {
                    if (wasClosed) cnn.Open();
                    using (var cmd = command.SetupCommand(cnn, null))
                    {
                        string masterSql = null;
                        foreach (var obj in multiExec)
                        {
                            if (isFirst)
                            {
                                masterSql = cmd.CommandText;
                                isFirst = false;
                                identity = new Identity(command.CommandText, cmd.CommandType, cnn, null, obj.GetType(), null);
                                info = GetCacheInfo(identity, obj, command.AddToCache);
                            }
                            else
                            {
                                cmd.CommandText = masterSql; // because we do magic replaces on "in" etc
                                cmd.Parameters.Clear(); // current code is Add-tastic
                            }
                            info.ParamReader(cmd, obj);
                            total += cmd.ExecuteNonQuery();
                        }
                    }
                    command.OnCompleted();
                } finally
                {
                    if (wasClosed) cnn.Close();
                }
                return total;
            }

            // nice and simple
            if (param != null)
            {
                identity = new Identity(command.CommandText, command.CommandType, cnn, null, param.GetType(), null);
                info = GetCacheInfo(identity, param, command.AddToCache);
            }
            return ExecuteCommand(cnn, ref command, param == null ? null : info.ParamReader);
        }

        /// <summary>
        /// Execute parameterized SQL and return an <see cref="IDataReader"/>
        /// </summary>
        /// <returns>An <see cref="IDataReader"/> that can be used to iterate over the results of the SQL query.</returns>
        /// <remarks>
        /// This is typically used when the results of a query are not processed by Dapper, for example, used to fill a <see cref="DataTable"/>
        /// or <see cref="DataSet"/>.
        /// </remarks>
        /// <example>
        /// <code>
        /// <![CDATA[
        /// DataTable table = new DataTable("MyTable");
        /// using (var reader = ExecuteReader(cnn, sql, param))
        /// {
        ///     table.Load(reader);
        /// }
        /// ]]>
        /// </code>
        /// </example>
        public static IDataReader ExecuteReader(
#if CSHARP30
this IDbConnection cnn, string sql, object param, IDbTransaction transaction, int? commandTimeout, CommandType? commandType
#else
this IDbConnection cnn, string sql, object param = null, IDbTransaction transaction = null, int? commandTimeout = null, CommandType? commandType = null
#endif
)
        {
            var command = new CommandDefinition(sql, (object)param, transaction, commandTimeout, commandType, CommandFlags.Buffered);
            IDbCommand dbcmd;
            var reader = ExecuteReaderImpl(cnn, ref command, CommandBehavior.Default, out dbcmd);
            return new WrappedReader(dbcmd, reader);
        }

        /// <summary>
        /// Execute parameterized SQL and return an <see cref="IDataReader"/>
        /// </summary>
        /// <returns>An <see cref="IDataReader"/> that can be used to iterate over the results of the SQL query.</returns>
        /// <remarks>
        /// This is typically used when the results of a query are not processed by Dapper, for example, used to fill a <see cref="DataTable"/>
        /// or <see cref="DataSet"/>.
        /// </remarks>
        public static IDataReader ExecuteReader(this IDbConnection cnn, CommandDefinition command)
        {
            IDbCommand dbcmd;
            var reader = ExecuteReaderImpl(cnn, ref command, CommandBehavior.Default, out dbcmd);
            return new WrappedReader(dbcmd, reader);
        }
        /// <summary>
        /// Execute parameterized SQL and return an <see cref="IDataReader"/>
        /// </summary>
        /// <returns>An <see cref="IDataReader"/> that can be used to iterate over the results of the SQL query.</returns>
        /// <remarks>
        /// This is typically used when the results of a query are not processed by Dapper, for example, used to fill a <see cref="DataTable"/>
        /// or <see cref="DataSet"/>.
        /// </remarks>
        public static IDataReader ExecuteReader(this IDbConnection cnn, CommandDefinition command, CommandBehavior commandBehavior)
        {
            IDbCommand dbcmd;
            var reader = ExecuteReaderImpl(cnn, ref command, commandBehavior, out dbcmd);
            return new WrappedReader(dbcmd, reader);
        }

#if !CSHARP30
        /// <summary>
        /// Return a list of dynamic objects, reader is closed after the call
        /// </summary>
        /// <remarks>Note: each row can be accessed via "dynamic", or by casting to an IDictionary&lt;string,object&gt;</remarks>
        public static IEnumerable<dynamic> Query(this IDbConnection cnn, string sql, object param = null, IDbTransaction transaction = null, bool buffered = true, int? commandTimeout = null, CommandType? commandType = null)
        {
            return Query<DapperRow>(cnn, sql, param as object, transaction, buffered, commandTimeout, commandType);
        }
#else
        /// <summary>
        /// Return a list of dynamic objects, reader is closed after the call
        /// </summary>
        public static IEnumerable<IDictionary<string, object>> Query(this IDbConnection cnn, string sql, object param)
        {
            return Query(cnn, sql, param, null, true, null, null);
        }

        /// <summary>
        /// Return a list of dynamic objects, reader is closed after the call
        /// </summary>
        public static IEnumerable<IDictionary<string, object>> Query(this IDbConnection cnn, string sql, object param, IDbTransaction transaction)
        {
            return Query(cnn, sql, param, transaction, true, null, null);
        }

        /// <summary>
        /// Return a list of dynamic objects, reader is closed after the call
        /// </summary>
        public static IEnumerable<IDictionary<string, object>> Query(this IDbConnection cnn, string sql, object param, CommandType? commandType)
        {
            return Query(cnn, sql, param, null, true, null, commandType);
        }

        /// <summary>
        /// Return a list of dynamic objects, reader is closed after the call
        /// </summary>
        public static IEnumerable<IDictionary<string, object>> Query(this IDbConnection cnn, string sql, object param, IDbTransaction transaction, CommandType? commandType)
        {
            return Query(cnn, sql, param, transaction, true, null, commandType);
        }

        /// <summary>
        /// Return a list of dynamic objects, reader is closed after the call
        /// </summary>
        public static IEnumerable<IDictionary<string, object>> Query(this IDbConnection cnn, string sql, object param, IDbTransaction transaction, bool buffered, int? commandTimeout, CommandType? commandType)
        {
            return Query<IDictionary<string, object>>(cnn, sql, param, transaction, buffered, commandTimeout, commandType);
        }
#endif

        /// <summary>
        /// Executes a query, returning the data typed as per T
        /// </summary>
        /// <remarks>the dynamic param may seem a bit odd, but this works around a major usability issue in vs, if it is Object vs completion gets annoying. Eg type new [space] get new object</remarks>
        /// <returns>A sequence of data of the supplied type; if a basic type (int, string, etc) is queried then the data from the first column in assumed, otherwise an instance is
        /// created per row, and a direct column-name===member-name mapping is assumed (case insensitive).
        /// </returns>
        public static IEnumerable<T> Query<T>(
#if CSHARP30
this IDbConnection cnn, string sql, object param, IDbTransaction transaction, bool buffered, int? commandTimeout, CommandType? commandType
#else
this IDbConnection cnn, string sql, object param = null, IDbTransaction transaction = null, bool buffered = true, int? commandTimeout = null, CommandType? commandType = null
#endif
)
        {
            var command = new CommandDefinition(sql, (object)param, transaction, commandTimeout, commandType, buffered ? CommandFlags.Buffered : CommandFlags.None);
            var data = QueryImpl<T>(cnn, command, typeof(T));
            return command.Buffered ? data.ToList() : data;
        }

        /// <summary>
        /// Executes a query, returning the data typed as per the Type suggested
        /// </summary>
        /// <returns>A sequence of data of the supplied type; if a basic type (int, string, etc) is queried then the data from the first column in assumed, otherwise an instance is
        /// created per row, and a direct column-name===member-name mapping is assumed (case insensitive).
        /// </returns>
        public static IEnumerable<object> Query(
#if CSHARP30
this IDbConnection cnn, Type type, string sql, object param, IDbTransaction transaction, bool buffered, int? commandTimeout, CommandType? commandType
#else
this IDbConnection cnn, Type type, string sql, object param = null, IDbTransaction transaction = null, bool buffered = true, int? commandTimeout = null, CommandType? commandType = null
#endif
        )
        {
            if (type == null) throw new ArgumentNullException("type");
            var command = new CommandDefinition(sql, (object)param, transaction, commandTimeout, commandType, buffered ? CommandFlags.Buffered : CommandFlags.None);
            var data = QueryImpl<object>(cnn, command, type);
            return command.Buffered ? data.ToList() : data;
        }
        /// <summary>
        /// Executes a query, returning the data typed as per T
        /// </summary>
        /// <remarks>the dynamic param may seem a bit odd, but this works around a major usability issue in vs, if it is Object vs completion gets annoying. Eg type new [space] get new object</remarks>
        /// <returns>A sequence of data of the supplied type; if a basic type (int, string, etc) is queried then the data from the first column in assumed, otherwise an instance is
        /// created per row, and a direct column-name===member-name mapping is assumed (case insensitive).
        /// </returns>
        public static IEnumerable<T> Query<T>(this IDbConnection cnn, CommandDefinition command)
        {
            var data = QueryImpl<T>(cnn, command, typeof(T));
            return command.Buffered ? data.ToList() : data;
        }



        /// <summary>
        /// Execute a command that returns multiple result sets, and access each in turn
        /// </summary>
        public static GridReader QueryMultiple(
#if CSHARP30
this IDbConnection cnn, string sql, object param, IDbTransaction transaction, int? commandTimeout, CommandType? commandType
#else
            this IDbConnection cnn, string sql, object param = null, IDbTransaction transaction = null, int? commandTimeout = null, CommandType? commandType = null
#endif
)
        {
            var command = new CommandDefinition(sql, (object)param, transaction, commandTimeout, commandType, CommandFlags.Buffered);
            return QueryMultipleImpl(cnn, ref command);
        }
        /// <summary>
        /// Execute a command that returns multiple result sets, and access each in turn
        /// </summary>
        public static GridReader QueryMultiple(this IDbConnection cnn, CommandDefinition command)
        {
            return QueryMultipleImpl(cnn, ref command);
        }
        private static GridReader QueryMultipleImpl(this IDbConnection cnn, ref CommandDefinition command)
        {
            object param = command.Parameters;
            Identity identity = new Identity(command.CommandText, command.CommandType, cnn, typeof(GridReader), param == null ? null : param.GetType(), null);
            CacheInfo info = GetCacheInfo(identity, param, command.AddToCache);

            IDbCommand cmd = null;
            IDataReader reader = null;
            bool wasClosed = cnn.State == ConnectionState.Closed;
            try
            {
                if (wasClosed) cnn.Open();
                cmd = command.SetupCommand(cnn, info.ParamReader);
                reader = cmd.ExecuteReader(wasClosed ? CommandBehavior.CloseConnection | CommandBehavior.SequentialAccess : CommandBehavior.SequentialAccess);

                var result = new GridReader(cmd, reader, identity, command.Parameters as DynamicParameters, command.AddToCache);
                cmd = null; // now owned by result
                wasClosed = false; // *if* the connection was closed and we got this far, then we now have a reader
                // with the CloseConnection flag, so the reader will deal with the connection; we
                // still need something in the "finally" to ensure that broken SQL still results
                // in the connection closing itself
                return result;
            }
            catch
            {
                if (reader != null)
                {
                    if (!reader.IsClosed) try { cmd.Cancel(); }
                        catch { /* don't spoil the existing exception */ }
                    reader.Dispose();
                }
                if (cmd != null) cmd.Dispose();
                if (wasClosed) cnn.Close();
                throw;
            }
        }

        private static IEnumerable<T> QueryImpl<T>(this IDbConnection cnn, CommandDefinition command, Type effectiveType)
        {
            object param = command.Parameters;
            var identity = new Identity(command.CommandText, command.CommandType, cnn, effectiveType, param == null ? null : param.GetType(), null);
            var info = GetCacheInfo(identity, param, command.AddToCache);

            IDbCommand cmd = null;
            IDataReader reader = null;

            bool wasClosed = cnn.State == ConnectionState.Closed;
            try
            {
                cmd = command.SetupCommand(cnn, info.ParamReader);

                if (wasClosed) cnn.Open();
                reader = cmd.ExecuteReader(wasClosed ? CommandBehavior.CloseConnection | CommandBehavior.SequentialAccess : CommandBehavior.SequentialAccess);
                wasClosed = false; // *if* the connection was closed and we got this far, then we now have a reader
                // with the CloseConnection flag, so the reader will deal with the connection; we
                // still need something in the "finally" to ensure that broken SQL still results
                // in the connection closing itself
                var tuple = info.Deserializer;
                int hash = GetColumnHash(reader);
                if (tuple.Func == null || tuple.Hash != hash)
                {
                    if (reader.FieldCount == 0) //https://code.google.com/p/dapper-dot-net/issues/detail?id=57
                        yield break;
                    tuple = info.Deserializer = new DeserializerState(hash, GetDeserializer(effectiveType, reader, 0, -1, false));
                    if(command.AddToCache) SetQueryCache(identity, info);
                }

                var func = tuple.Func;
                var convertToType = Nullable.GetUnderlyingType(effectiveType) ?? effectiveType;
                while (reader.Read())
                {
                    object val = func(reader);
					if (val == null || val is T) {
                        yield return (T)val;
                    } else {
                        yield return (T)Convert.ChangeType(val, convertToType, CultureInfo.InvariantCulture);
                    }
                }
                while (reader.NextResult()) { }
                // happy path; close the reader cleanly - no
                // need for "Cancel" etc
                reader.Dispose();
                reader = null;

                command.OnCompleted();
            }
            finally
            {
                if (reader != null)
                {
                    if (!reader.IsClosed) try { cmd.Cancel(); }
                        catch { /* don't spoil the existing exception */ }
                    reader.Dispose();
                }
                if (wasClosed) cnn.Close();
                if (cmd != null) cmd.Dispose();
            }
        }

        /// <summary>
        /// Maps a query to objects
        /// </summary>
        /// <typeparam name="TFirst">The first type in the record set</typeparam>
        /// <typeparam name="TSecond">The second type in the record set</typeparam>
        /// <typeparam name="TReturn">The return type</typeparam>
        /// <param name="cnn"></param>
        /// <param name="sql"></param>
        /// <param name="map"></param>
        /// <param name="param"></param>
        /// <param name="transaction"></param>
        /// <param name="buffered"></param>
        /// <param name="splitOn">The Field we should split and read the second object from (default: id)</param>
        /// <param name="commandTimeout">Number of seconds before command execution timeout</param>
        /// <param name="commandType">Is it a stored proc or a batch?</param>
        /// <returns></returns>
        public static IEnumerable<TReturn> Query<TFirst, TSecond, TReturn>(
#if CSHARP30
this IDbConnection cnn, string sql, Func<TFirst, TSecond, TReturn> map, object param, IDbTransaction transaction, bool buffered, string splitOn, int? commandTimeout, CommandType? commandType
#else
this IDbConnection cnn, string sql, Func<TFirst, TSecond, TReturn> map, object param = null, IDbTransaction transaction = null, bool buffered = true, string splitOn = "Id", int? commandTimeout = null, CommandType? commandType = null
#endif
)
        {
            return MultiMap<TFirst, TSecond, DontMap, DontMap, DontMap, DontMap, DontMap, TReturn>(cnn, sql, map, param as object, transaction, buffered, splitOn, commandTimeout, commandType);
        }

        /// <summary>
        /// Maps a query to objects
        /// </summary>
        /// <typeparam name="TFirst"></typeparam>
        /// <typeparam name="TSecond"></typeparam>
        /// <typeparam name="TThird"></typeparam>
        /// <typeparam name="TReturn"></typeparam>
        /// <param name="cnn"></param>
        /// <param name="sql"></param>
        /// <param name="map"></param>
        /// <param name="param"></param>
        /// <param name="transaction"></param>
        /// <param name="buffered"></param>
        /// <param name="splitOn">The Field we should split and read the second object from (default: id)</param>
        /// <param name="commandTimeout">Number of seconds before command execution timeout</param>
        /// <param name="commandType"></param>
        /// <returns></returns>
        public static IEnumerable<TReturn> Query<TFirst, TSecond, TThird, TReturn>(
#if CSHARP30
this IDbConnection cnn, string sql, Func<TFirst, TSecond, TThird, TReturn> map, object param, IDbTransaction transaction, bool buffered, string splitOn, int? commandTimeout, CommandType? commandType
#else
this IDbConnection cnn, string sql, Func<TFirst, TSecond, TThird, TReturn> map, object param = null, IDbTransaction transaction = null, bool buffered = true, string splitOn = "Id", int? commandTimeout = null, CommandType? commandType = null
#endif
)
        {
            return MultiMap<TFirst, TSecond, TThird, DontMap, DontMap, DontMap, DontMap, TReturn>(cnn, sql, map, param as object, transaction, buffered, splitOn, commandTimeout, commandType);
        }

        /// <summary>
        /// Perform a multi mapping query with 4 input parameters
        /// </summary>
        /// <typeparam name="TFirst"></typeparam>
        /// <typeparam name="TSecond"></typeparam>
        /// <typeparam name="TThird"></typeparam>
        /// <typeparam name="TFourth"></typeparam>
        /// <typeparam name="TReturn"></typeparam>
        /// <param name="cnn"></param>
        /// <param name="sql"></param>
        /// <param name="map"></param>
        /// <param name="param"></param>
        /// <param name="transaction"></param>
        /// <param name="buffered"></param>
        /// <param name="splitOn"></param>
        /// <param name="commandTimeout"></param>
        /// <param name="commandType"></param>
        /// <returns></returns>
        public static IEnumerable<TReturn> Query<TFirst, TSecond, TThird, TFourth, TReturn>(
#if CSHARP30
this IDbConnection cnn, string sql, Func<TFirst, TSecond, TThird, TFourth, TReturn> map, object param, IDbTransaction transaction, bool buffered, string splitOn, int? commandTimeout, CommandType? commandType
#else
this IDbConnection cnn, string sql, Func<TFirst, TSecond, TThird, TFourth, TReturn> map, object param = null, IDbTransaction transaction = null, bool buffered = true, string splitOn = "Id", int? commandTimeout = null, CommandType? commandType = null
#endif
)
        {
            return MultiMap<TFirst, TSecond, TThird, TFourth, DontMap, DontMap, DontMap, TReturn>(cnn, sql, map, param as object, transaction, buffered, splitOn, commandTimeout, commandType);
        }

#if !CSHARP30
        /// <summary>
        /// Perform a multi mapping query with 5 input parameters
        /// </summary>
        /// <typeparam name="TFirst"></typeparam>
        /// <typeparam name="TSecond"></typeparam>
        /// <typeparam name="TThird"></typeparam>
        /// <typeparam name="TFourth"></typeparam>
        /// <typeparam name="TFifth"></typeparam>
        /// <typeparam name="TReturn"></typeparam>
        /// <param name="cnn"></param>
        /// <param name="sql"></param>
        /// <param name="map"></param>
        /// <param name="param"></param>
        /// <param name="transaction"></param>
        /// <param name="buffered"></param>
        /// <param name="splitOn"></param>
        /// <param name="commandTimeout"></param>
        /// <param name="commandType"></param>
        /// <returns></returns>
        public static IEnumerable<TReturn> Query<TFirst, TSecond, TThird, TFourth, TFifth, TReturn>(
            this IDbConnection cnn, string sql, Func<TFirst, TSecond, TThird, TFourth, TFifth, TReturn> map, object param = null, IDbTransaction transaction = null, bool buffered = true, string splitOn = "Id", int? commandTimeout = null, CommandType? commandType = null
)
        {
            return MultiMap<TFirst, TSecond, TThird, TFourth, TFifth, DontMap, DontMap, TReturn>(cnn, sql, map, param as object, transaction, buffered, splitOn, commandTimeout, commandType);
        }

        /// <summary>
        /// Perform a multi mapping query with 6 input parameters
        /// </summary>
        /// <typeparam name="TFirst"></typeparam>
        /// <typeparam name="TSecond"></typeparam>
        /// <typeparam name="TThird"></typeparam>
        /// <typeparam name="TFourth"></typeparam>
        /// <typeparam name="TFifth"></typeparam>
        /// <typeparam name="TSixth"></typeparam>
        /// <typeparam name="TReturn"></typeparam>
        /// <param name="cnn"></param>
        /// <param name="sql"></param>
        /// <param name="map"></param>
        /// <param name="param"></param>
        /// <param name="transaction"></param>
        /// <param name="buffered"></param>
        /// <param name="splitOn"></param>
        /// <param name="commandTimeout"></param>
        /// <param name="commandType"></param>
        /// <returns></returns>
        public static IEnumerable<TReturn> Query<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TReturn>(
            this IDbConnection cnn, string sql, Func<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TReturn> map, object param = null, IDbTransaction transaction = null, bool buffered = true, string splitOn = "Id", int? commandTimeout = null, CommandType? commandType = null
)
        {
            return MultiMap<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, DontMap, TReturn>(cnn, sql, map, param as object, transaction, buffered, splitOn, commandTimeout, commandType);
        }


        /// <summary>
        /// Perform a multi mapping query with 7 input parameters
        /// </summary>
        /// <typeparam name="TFirst"></typeparam>
        /// <typeparam name="TSecond"></typeparam>
        /// <typeparam name="TThird"></typeparam>
        /// <typeparam name="TFourth"></typeparam>
        /// <typeparam name="TFifth"></typeparam>
        /// <typeparam name="TSixth"></typeparam>
        /// <typeparam name="TSeventh"></typeparam>
        /// <typeparam name="TReturn"></typeparam>
        /// <param name="cnn"></param>
        /// <param name="sql"></param>
        /// <param name="map"></param>
        /// <param name="param"></param>
        /// <param name="transaction"></param>
        /// <param name="buffered"></param>
        /// <param name="splitOn"></param>
        /// <param name="commandTimeout"></param>
        /// <param name="commandType"></param>
        /// <returns></returns>
        public static IEnumerable<TReturn> Query<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TSeventh, TReturn>(this IDbConnection cnn, string sql, Func<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TSeventh, TReturn> map, object param = null, IDbTransaction transaction = null, bool buffered = true, string splitOn = "Id", int? commandTimeout = null, CommandType? commandType = null)
        {
            return MultiMap<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TSeventh, TReturn>(cnn, sql, map, param as object, transaction, buffered, splitOn, commandTimeout, commandType);
        }

        /// <summary>
        /// Perform a multi mapping query with arbitrary input parameters
        /// </summary>
        /// <typeparam name="TReturn">The return type</typeparam>
        /// <param name="cnn"></param>
        /// <param name="sql"></param>
        /// <param name="types">array of types in the record set</param>
        /// <param name="map"></param>
        /// <param name="param"></param>
        /// <param name="transaction"></param>
        /// <param name="buffered"></param>
        /// <param name="splitOn">The Field we should split and read the second object from (default: id)</param>
        /// <param name="commandTimeout">Number of seconds before command execution timeout</param>
        /// <param name="commandType">Is it a stored proc or a batch?</param>
        /// <returns></returns>
        public static IEnumerable<TReturn> Query<TReturn>(this IDbConnection cnn, string sql, Type[] types, Func<object[], TReturn> map, dynamic param = null, IDbTransaction transaction = null, bool buffered = true, string splitOn = "Id", int? commandTimeout = null, CommandType? commandType = null)
        {
            var command = new CommandDefinition(sql, (object)param, transaction, commandTimeout, commandType, buffered ? CommandFlags.Buffered : CommandFlags.None);
            var results = MultiMapImpl<TReturn>(cnn, command, types, map, splitOn, null, null, true);
            return buffered ? results.ToList() : results;
        }
#endif
        partial class DontMap { }
        static IEnumerable<TReturn> MultiMap<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TSeventh, TReturn>(
            this IDbConnection cnn, string sql, Delegate map, object param, IDbTransaction transaction, bool buffered, string splitOn, int? commandTimeout, CommandType? commandType)
        {
            var command = new CommandDefinition(sql, (object)param, transaction, commandTimeout, commandType, buffered ? CommandFlags.Buffered : CommandFlags.None);
            var results = MultiMapImpl<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TSeventh, TReturn>(cnn, command, map, splitOn, null, null, true);
            return buffered ? results.ToList() : results;
        }

        static IEnumerable<TReturn> MultiMapImpl<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TSeventh, TReturn>(this IDbConnection cnn, CommandDefinition command, Delegate map, string splitOn, IDataReader reader, Identity identity, bool finalize)
        {
            object param = command.Parameters;
            identity = identity ?? new Identity(command.CommandText, command.CommandType, cnn, typeof(TFirst), param == null ? null : param.GetType(), new[] { typeof(TFirst), typeof(TSecond), typeof(TThird), typeof(TFourth), typeof(TFifth), typeof(TSixth), typeof(TSeventh) });
            CacheInfo cinfo = GetCacheInfo(identity, param, command.AddToCache);

            IDbCommand ownedCommand = null;
            IDataReader ownedReader = null;

            bool wasClosed = cnn != null && cnn.State == ConnectionState.Closed;
            try
            {
                if (reader == null)
                {
                    ownedCommand = command.SetupCommand(cnn, cinfo.ParamReader);
                    if (wasClosed) cnn.Open();
                    ownedReader = ownedCommand.ExecuteReader(wasClosed ? CommandBehavior.CloseConnection | CommandBehavior.SequentialAccess : CommandBehavior.SequentialAccess);
                    reader = ownedReader;
                }
                DeserializerState deserializer = default(DeserializerState);
                Func<IDataReader, object>[] otherDeserializers = null;

                int hash = GetColumnHash(reader);
                if ((deserializer = cinfo.Deserializer).Func == null || (otherDeserializers = cinfo.OtherDeserializers) == null || hash != deserializer.Hash)
                {
                    var deserializers = GenerateDeserializers(new Type[] { typeof(TFirst), typeof(TSecond), typeof(TThird), typeof(TFourth), typeof(TFifth), typeof(TSixth), typeof(TSeventh) }, splitOn, reader);
                    deserializer = cinfo.Deserializer = new DeserializerState(hash, deserializers[0]);
                    otherDeserializers = cinfo.OtherDeserializers = deserializers.Skip(1).ToArray();
                    if(command.AddToCache) SetQueryCache(identity, cinfo);
                }

                Func<IDataReader, TReturn> mapIt = GenerateMapper<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TSeventh, TReturn>(deserializer.Func, otherDeserializers, map);

                if (mapIt != null)
                {
                    while (reader.Read())
                    {
                        yield return mapIt(reader);
                    }
                    if(finalize)
                    {
                        while (reader.NextResult()) { }
                        command.OnCompleted();
                    }                    
                }
            }
            finally
            {
                try
                {
                    if (ownedReader != null)
                    {
                        ownedReader.Dispose();
                    }
                }
                finally
                {
                    if (ownedCommand != null)
                    {
                        ownedCommand.Dispose();
                    }
                    if (wasClosed) cnn.Close();
                }
            }
        }

        static IEnumerable<TReturn> MultiMapImpl<TReturn>(this IDbConnection cnn, CommandDefinition command, Type[] types, Func<object[], TReturn> map, string splitOn, IDataReader reader, Identity identity, bool finalize)
        {
            if (types.Length < 1)
            {
                throw new ArgumentException("you must provide at least one type to deserialize");
            }

            object param = command.Parameters;
            identity = identity ?? new Identity(command.CommandText, command.CommandType, cnn, types[0], param == null ? null : param.GetType(), types);
            CacheInfo cinfo = GetCacheInfo(identity, param, command.AddToCache);

            IDbCommand ownedCommand = null;
            IDataReader ownedReader = null;

            bool wasClosed = cnn != null && cnn.State == ConnectionState.Closed;
            try
            {
                if (reader == null)
                {
                    ownedCommand = command.SetupCommand(cnn, cinfo.ParamReader);
                    if (wasClosed) cnn.Open();
                    ownedReader = ownedCommand.ExecuteReader();
                    reader = ownedReader;
                }
                DeserializerState deserializer = default(DeserializerState);
                Func<IDataReader, object>[] otherDeserializers = null;

                int hash = GetColumnHash(reader);
                if ((deserializer = cinfo.Deserializer).Func == null || (otherDeserializers = cinfo.OtherDeserializers) == null || hash != deserializer.Hash)
                {
                    var deserializers = GenerateDeserializers(types, splitOn, reader);
                    deserializer = cinfo.Deserializer = new DeserializerState(hash, deserializers[0]);
                    otherDeserializers = cinfo.OtherDeserializers = deserializers.Skip(1).ToArray();
                    SetQueryCache(identity, cinfo);
                }

                Func<IDataReader, TReturn> mapIt = GenerateMapper(types.Length, deserializer.Func, otherDeserializers, map);

                if (mapIt != null)
                {
                    while (reader.Read())
                    {
                        yield return mapIt(reader);
                    }
                    if (finalize)
                    {
                        while (reader.NextResult()) { }
                        command.OnCompleted();
                    }
                }
            }
            finally
            {
                try
                {
                    if (ownedReader != null)
                    {
                        ownedReader.Dispose();
                    }
                }
                finally
                {
                    if (ownedCommand != null)
                    {
                        ownedCommand.Dispose();
                    }
                    if (wasClosed) cnn.Close();
                }
            }
        }

        private static Func<IDataReader, TReturn> GenerateMapper<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TSeventh, TReturn>(Func<IDataReader, object> deserializer, Func<IDataReader, object>[] otherDeserializers, object map)
        {
            switch (otherDeserializers.Length)
            {
                case 1:
                    return r => ((Func<TFirst, TSecond, TReturn>)map)((TFirst)deserializer(r), (TSecond)otherDeserializers[0](r));
                case 2:
                    return r => ((Func<TFirst, TSecond, TThird, TReturn>)map)((TFirst)deserializer(r), (TSecond)otherDeserializers[0](r), (TThird)otherDeserializers[1](r));
                case 3:
                    return r => ((Func<TFirst, TSecond, TThird, TFourth, TReturn>)map)((TFirst)deserializer(r), (TSecond)otherDeserializers[0](r), (TThird)otherDeserializers[1](r), (TFourth)otherDeserializers[2](r));
#if !CSHARP30
                case 4:
                    return r => ((Func<TFirst, TSecond, TThird, TFourth, TFifth, TReturn>)map)((TFirst)deserializer(r), (TSecond)otherDeserializers[0](r), (TThird)otherDeserializers[1](r), (TFourth)otherDeserializers[2](r), (TFifth)otherDeserializers[3](r));
                case 5:
                    return r => ((Func<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TReturn>)map)((TFirst)deserializer(r), (TSecond)otherDeserializers[0](r), (TThird)otherDeserializers[1](r), (TFourth)otherDeserializers[2](r), (TFifth)otherDeserializers[3](r), (TSixth)otherDeserializers[4](r));
                case 6:
                    return r => ((Func<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TSeventh, TReturn>)map)((TFirst)deserializer(r), (TSecond)otherDeserializers[0](r), (TThird)otherDeserializers[1](r), (TFourth)otherDeserializers[2](r), (TFifth)otherDeserializers[3](r), (TSixth)otherDeserializers[4](r), (TSeventh)otherDeserializers[5](r));
#endif
                default:
                    throw new NotSupportedException();
            }
        }

        private static Func<IDataReader, TReturn> GenerateMapper<TReturn>(int length, Func<IDataReader, object> deserializer, Func<IDataReader, object>[] otherDeserializers, Func<object[], TReturn> map)
        {
            return r =>
            {
                var objects = new object[length];
                objects[0] = deserializer(r);

                for (var i = 1; i < length; ++i)
                {
                    objects[i] = otherDeserializers[i - 1](r);
                }

                return map(objects);
            };
        }

        private static Func<IDataReader, object>[] GenerateDeserializers(Type[] types, string splitOn, IDataReader reader)
        {
            var deserializers = new List<Func<IDataReader, object>>();
            var splits = splitOn.Split(',').Select(s => s.Trim()).ToArray();
                bool isMultiSplit = splits.Length > 1;
            if (types.First() == typeof(Object))
            {
                // we go left to right for dynamic multi-mapping so that the madness of TestMultiMappingVariations
                // is supported
                bool first = true;
                int currentPos = 0;
                int splitIdx = 0;
                string currentSplit = splits[splitIdx];
                foreach (var type in types)
                {
                    if (type == typeof(DontMap))
                    {
                        break;
                    }

                    int splitPoint = GetNextSplitDynamic(currentPos, currentSplit, reader);
                    if (isMultiSplit && splitIdx < splits.Length - 1)
                    {
                        currentSplit = splits[++splitIdx];
                    }
                    deserializers.Add((GetDeserializer(type, reader, currentPos, splitPoint - currentPos, !first)));
                    currentPos = splitPoint;
                    first = false;
                }
            }
            else
            {
                // in this we go right to left through the data reader in order to cope with properties that are
                // named the same as a subsequent primary key that we split on
                int currentPos = reader.FieldCount;
                int splitIdx = splits.Length - 1;
                var currentSplit = splits[splitIdx];
                for (var typeIdx = types.Length - 1; typeIdx >= 0; --typeIdx)
                {
                    var type = types[typeIdx];
                    if (type == typeof (DontMap))
                    {
                        continue;
                    }

                    int splitPoint = 0;
                    if (typeIdx > 0)
                    {
                        splitPoint = GetNextSplit(currentPos, currentSplit, reader);
                        if (isMultiSplit && splitIdx > 0)
                        {
                            currentSplit = splits[--splitIdx];
                        }
                    }

                    deserializers.Add((GetDeserializer(type, reader, splitPoint, currentPos - splitPoint, typeIdx > 0)));
                    currentPos = splitPoint;
                }

                deserializers.Reverse();

            }
            return deserializers.ToArray();
        }

        private static int GetNextSplitDynamic(int startIdx, string splitOn, IDataReader reader)
        {
            if (startIdx == reader.FieldCount)
            {
                throw MultiMapException(reader);
            }

            if (splitOn == "*")
            {
                return ++startIdx;
            }

            for (var i = startIdx + 1; i < reader.FieldCount; ++i)
            {
                if (string.Equals(splitOn, reader.GetName(i), StringComparison.OrdinalIgnoreCase))
                {
                    return i;
                }
            }

            return reader.FieldCount;
        }

        private static int GetNextSplit(int startIdx, string splitOn, IDataReader reader)
        {
            if (splitOn == "*")
            {
                return --startIdx;
            }

            for (var i = startIdx - 1; i > 0; --i)
            {
                if (string.Equals(splitOn, reader.GetName(i), StringComparison.OrdinalIgnoreCase))
                {
                    return i;
                }
            }

            throw MultiMapException(reader);
        }

        private static CacheInfo GetCacheInfo(Identity identity, object exampleParameters, bool addToCache)
        {
            CacheInfo info;
            if (!TryGetQueryCache(identity, out info))
            {
                info = new CacheInfo();
                if (identity.parametersType != null)
                {
                    Action<IDbCommand, object> reader;
                    if (exampleParameters is IDynamicParameters)
                    {
                        reader = (cmd, obj) => { ((IDynamicParameters)obj).AddParameters(cmd, identity); };
                    }
                    else if (exampleParameters is IEnumerable<KeyValuePair<string, object>>)
                    {
                        reader = (cmd, obj) =>
                        {
                            IDynamicParameters mapped = new DynamicParameters(obj);
                            mapped.AddParameters(cmd, identity);
                        };
                    }
                    else
                    {
                        var literals = GetLiteralTokens(identity.sql);
                        reader = CreateParamInfoGenerator(identity, false, true, literals);
                    }
                    if((identity.commandType == null || identity.commandType == CommandType.Text) && ShouldPassByPosition(identity.sql))
                    {
                        var tail = reader;
                        var sql = identity.sql;
                        reader = (cmd, obj) =>
                        {
                            tail(cmd, obj);
                            PassByPosition(cmd);
                        };
                    }
                    info.ParamReader = reader;
                }
                if(addToCache) SetQueryCache(identity, info);
            }
            return info;
        }

        private static bool ShouldPassByPosition(string sql)
        {
            return sql != null && sql.IndexOf('?') >= 0 && pseudoPositional.IsMatch(sql);
        }

        private static void PassByPosition(IDbCommand cmd)
        {
            if (cmd.Parameters.Count == 0) return;

            Dictionary<string, IDbDataParameter> parameters = new Dictionary<string, IDbDataParameter>(StringComparer.Ordinal);
            
            foreach(IDbDataParameter param in cmd.Parameters)
            {
                if (!string.IsNullOrEmpty(param.ParameterName)) parameters[param.ParameterName] = param;
            }
            HashSet<string> consumed = new HashSet<string>(StringComparer.Ordinal);
            bool firstMatch = true;
            cmd.CommandText = pseudoPositional.Replace(cmd.CommandText, match =>
            {
                string key = match.Groups[1].Value;
                IDbDataParameter param;
                if (!consumed.Add(key))
                {
                    throw new InvalidOperationException("When passing parameters by position, each parameter can only be referenced once");
                }
                else if (parameters.TryGetValue(key, out param))
                {
                    if(firstMatch)
                    {
                        firstMatch = false;
                        cmd.Parameters.Clear(); // only clear if we are pretty positive that we've found this pattern successfully
                    }
                    // if found, return the anonymous token "?"
                    cmd.Parameters.Add(param);
                    parameters.Remove(key);
                    consumed.Add(key);
                    return "?";
                }
                else
                {
                    // otherwise, leave alone for simple debugging
                    return match.Value;
                }
            });
        }

        private static Func<IDataReader, object> GetDeserializer(Type type, IDataReader reader, int startBound, int length, bool returnNullIfFirstMissing)
        {
#if !CSHARP30
            // dynamic is passed in as Object ... by c# design
            if (type == typeof(object)
                || type == typeof(DapperRow))
            {
                return GetDapperRowDeserializer(reader, startBound, length, returnNullIfFirstMissing);
            }
#else
            if (type.IsAssignableFrom(typeof(Dictionary<string, object>)))
            {
                return GetDictionaryDeserializer(reader, startBound, length, returnNullIfFirstMissing);
            }
#endif
            Type underlyingType = null;
            if (!(typeMap.ContainsKey(type) || type.IsEnum() || type.FullName == LinqBinary ||
                (type.IsValueType()  && (underlyingType = Nullable.GetUnderlyingType(type)) != null && underlyingType.IsEnum())))
            {
                ITypeHandler handler;
                if (typeHandlers.TryGetValue(type, out handler))
                {
                    return GetHandlerDeserializer(handler, type, startBound);
                }
                return GetTypeDeserializer(type, reader, startBound, length, returnNullIfFirstMissing);
            }
            return GetStructDeserializer(type, underlyingType ?? type, startBound);
        }
        static Func<IDataReader, object> GetHandlerDeserializer(ITypeHandler handler, Type type, int startBound)
        {
            return (IDataReader reader) =>
                handler.Parse(type, reader.GetValue(startBound));
        }

#if !CSHARP30
        private sealed partial class DapperTable
        {
            string[] fieldNames;
            readonly Dictionary<string, int> fieldNameLookup;

            internal string[] FieldNames { get { return fieldNames; } }

            public DapperTable(string[] fieldNames)
            {
                if (fieldNames == null) throw new ArgumentNullException("fieldNames");
                this.fieldNames = fieldNames;

                fieldNameLookup = new Dictionary<string, int>(fieldNames.Length, StringComparer.Ordinal);
                // if there are dups, we want the **first** key to be the "winner" - so iterate backwards
                for (int i = fieldNames.Length - 1; i >= 0; i--)
                {
                    string key = fieldNames[i];
                    if (key != null) fieldNameLookup[key] = i;
                }
            }

            internal int IndexOfName(string name)
            {
                int result;
                return (name != null && fieldNameLookup.TryGetValue(name, out result)) ? result : -1;
            }
            internal int AddField(string name)
            {
                if (name == null) throw new ArgumentNullException("name");
                if (fieldNameLookup.ContainsKey(name)) throw new InvalidOperationException("Field already exists: " + name);
                int oldLen = fieldNames.Length;
                Array.Resize(ref fieldNames, oldLen + 1); // yes, this is sub-optimal, but this is not the expected common case
                fieldNames[oldLen] = name;
                fieldNameLookup[name] = oldLen;
                return oldLen;
            }


            internal bool FieldExists(string key)
            {
                return key != null && fieldNameLookup.ContainsKey(key);
            }

            public int FieldCount { get { return fieldNames.Length; } }
        }

        sealed partial class DapperRowMetaObject : System.Dynamic.DynamicMetaObject
        {
            static readonly MethodInfo getValueMethod = typeof(IDictionary<string, object>).GetProperty("Item").GetGetMethod();
            static readonly MethodInfo setValueMethod = typeof(DapperRow).GetMethod("SetValue", new Type[] { typeof(string), typeof(object) });

            public DapperRowMetaObject(
                System.Linq.Expressions.Expression expression,
                System.Dynamic.BindingRestrictions restrictions
                )
                : base(expression, restrictions)
            {
            }

            public DapperRowMetaObject(
                System.Linq.Expressions.Expression expression,
                System.Dynamic.BindingRestrictions restrictions,
                object value
                )
                : base(expression, restrictions, value)
            {
            }

            System.Dynamic.DynamicMetaObject CallMethod(
                MethodInfo method,
                System.Linq.Expressions.Expression[] parameters
                )
            {
                var callMethod = new System.Dynamic.DynamicMetaObject(
                    System.Linq.Expressions.Expression.Call(
                        System.Linq.Expressions.Expression.Convert(Expression, LimitType),
                        method,
                        parameters),
                    System.Dynamic.BindingRestrictions.GetTypeRestriction(Expression, LimitType)
                    );
                return callMethod;
            }

            public override System.Dynamic.DynamicMetaObject BindGetMember(System.Dynamic.GetMemberBinder binder)
            {
                var parameters = new System.Linq.Expressions.Expression[]
                                     {
                                         System.Linq.Expressions.Expression.Constant(binder.Name)
                                     };

                var callMethod = CallMethod(getValueMethod, parameters);

                return callMethod;
            }

            // Needed for Visual basic dynamic support
            public override System.Dynamic.DynamicMetaObject BindInvokeMember(System.Dynamic.InvokeMemberBinder binder, System.Dynamic.DynamicMetaObject[] args)
            {
                var parameters = new System.Linq.Expressions.Expression[]
                                     {
                                         System.Linq.Expressions.Expression.Constant(binder.Name)
                                     };

                var callMethod = CallMethod(getValueMethod, parameters);

                return callMethod;
            }

            public override System.Dynamic.DynamicMetaObject BindSetMember(System.Dynamic.SetMemberBinder binder, System.Dynamic.DynamicMetaObject value)
            {
                var parameters = new System.Linq.Expressions.Expression[]
                                     {
                                         System.Linq.Expressions.Expression.Constant(binder.Name),
                                         value.Expression,
                                     };

                var callMethod = CallMethod(setValueMethod, parameters);

                return callMethod;
            }
        }

        private sealed partial class DapperRow
            : System.Dynamic.IDynamicMetaObjectProvider
            , IDictionary<string, object>
        {
            readonly DapperTable table;
            object[] values;

            public DapperRow(DapperTable table, object[] values)
            {
                if (table == null) throw new ArgumentNullException("table");
                if (values == null) throw new ArgumentNullException("values");
                this.table = table;
                this.values = values;
            }
            private sealed class DeadValue
            {
                public static readonly DeadValue Default = new DeadValue();
                private DeadValue() { }
            }
            int ICollection<KeyValuePair<string, object>>.Count
            {
                get
                {
                    int count = 0;
                    for (int i = 0; i < values.Length; i++)
                    {
                        if (!(values[i] is DeadValue)) count++;
                    }
                    return count;
                }
            }

            public bool TryGetValue(string name, out object value)
            {
                var index = table.IndexOfName(name);
                if (index < 0)
                { // doesn't exist
                    value = null;
                    return false;
                }
                // exists, **even if** we don't have a value; consider table rows heterogeneous
                value = index < values.Length ? values[index] : null;
                if (value is DeadValue)
                { // pretend it isn't here
                    value = null;
                    return false;
                }
                return true;
            }

            public override string ToString()
            {
                var sb = GetStringBuilder().Append("{DapperRow");
                foreach (var kv in this)
                {
                    var value = kv.Value;
                    sb.Append(", ").Append(kv.Key);
                    if (value != null)
                    {
                        sb.Append(" = '").Append(kv.Value).Append('\'');
                    }
                    else
                    {
                        sb.Append(" = NULL");
                    }
                }

                return sb.Append('}').__ToStringRecycle();
            }

            System.Dynamic.DynamicMetaObject System.Dynamic.IDynamicMetaObjectProvider.GetMetaObject(
                System.Linq.Expressions.Expression parameter)
            {
                return new DapperRowMetaObject(parameter, System.Dynamic.BindingRestrictions.Empty, this);
            }

            public IEnumerator<KeyValuePair<string, object>> GetEnumerator()
            {
                var names = table.FieldNames;
                for (var i = 0; i < names.Length; i++)
                {
                    object value = i < values.Length ? values[i] : null;
                    if (!(value is DeadValue))
                    {
                        yield return new KeyValuePair<string, object>(names[i], value);
                    }
                }
            }

            IEnumerator IEnumerable.GetEnumerator()
            {
                return GetEnumerator();
            }

#region Implementation of ICollection<KeyValuePair<string,object>>

            void ICollection<KeyValuePair<string, object>>.Add(KeyValuePair<string, object> item)
            {
                IDictionary<string, object> dic = this;
                dic.Add(item.Key, item.Value);
            }

            void ICollection<KeyValuePair<string, object>>.Clear()
            { // removes values for **this row**, but doesn't change the fundamental table
                for (int i = 0; i < values.Length; i++)
                    values[i] = DeadValue.Default;
            }

            bool ICollection<KeyValuePair<string, object>>.Contains(KeyValuePair<string, object> item)
            {
                object value;
                return TryGetValue(item.Key, out value) && Equals(value, item.Value);
            }

            void ICollection<KeyValuePair<string, object>>.CopyTo(KeyValuePair<string, object>[] array, int arrayIndex)
            {
                foreach (var kv in this)
                {
                    array[arrayIndex++] = kv; // if they didn't leave enough space; not our fault
                }
            }

            bool ICollection<KeyValuePair<string, object>>.Remove(KeyValuePair<string, object> item)
            {
                IDictionary<string, object> dic = this;
                return dic.Remove(item.Key);
            }

            bool ICollection<KeyValuePair<string, object>>.IsReadOnly
            {
                get { return false; }
            }

#endregion

#region Implementation of IDictionary<string,object>

            bool IDictionary<string, object>.ContainsKey(string key)
            {
                int index = table.IndexOfName(key);
                if (index < 0 || index >= values.Length || values[index] is DeadValue) return false;
                return true;
            }

            void IDictionary<string, object>.Add(string key, object value)
            {
                SetValue(key, value, true);
            }

            bool IDictionary<string, object>.Remove(string key)
            {
                int index = table.IndexOfName(key);
                if (index < 0 || index >= values.Length || values[index] is DeadValue) return false;
                values[index] = DeadValue.Default;
                return true;
            }

            object IDictionary<string, object>.this[string key]
            {
                get { object val; TryGetValue(key, out val); return val; }
                set { SetValue(key, value, false); }
            }

            public object SetValue(string key, object value)
            {
                return SetValue(key, value, false);
            }
            private object SetValue(string key, object value, bool isAdd)
            {
                if (key == null) throw new ArgumentNullException("key");
                int index = table.IndexOfName(key);
                if (index < 0)
                {
                    index = table.AddField(key);
                }
                else if (isAdd && index < values.Length && !(values[index] is DeadValue))
                {
                    // then semantically, this value already exists
                    throw new ArgumentException("An item with the same key has already been added", "key");
                }
                int oldLength = values.Length;
                if (oldLength <= index)
                {
                    // we'll assume they're doing lots of things, and
                    // grow it to the full width of the table
                    Array.Resize(ref values, table.FieldCount);
                    for (int i = oldLength; i < values.Length; i++)
                    {
                        values[i] = DeadValue.Default;
                    }
                }
                return values[index] = value;
            }

            ICollection<string> IDictionary<string, object>.Keys
            {
                get { return this.Select(kv => kv.Key).ToArray(); }
            }

            ICollection<object> IDictionary<string, object>.Values
            {
                get { return this.Select(kv => kv.Value).ToArray(); }
            }

#endregion
        }
#endif
        private static Exception MultiMapException(IDataRecord reader)
        {
            bool hasFields = false;
            try {
                hasFields = reader != null && reader.FieldCount != 0;
            } catch { }
            if (hasFields)
                return new ArgumentException("When using the multi-mapping APIs ensure you set the splitOn param if you have keys other than Id", "splitOn");
            else
                return new InvalidOperationException("No columns were selected");
        }
        
#if !CSHARP30
        internal static Func<IDataReader, object> GetDapperRowDeserializer(IDataRecord reader, int startBound, int length, bool returnNullIfFirstMissing)
        {
            var fieldCount = reader.FieldCount;
            if (length == -1)
            {
                length = fieldCount - startBound;
            }

            if (fieldCount <= startBound)
            {
                throw MultiMapException(reader);
            }

            var effectiveFieldCount = Math.Min(fieldCount - startBound, length);

            DapperTable table = null;

            return
                r =>
                {
                    if (table == null)
                    {
                        string[] names = new string[effectiveFieldCount];
                        for (int i = 0; i < effectiveFieldCount; i++)
                        {
                            names[i] = r.GetName(i + startBound);
                        }
                        table = new DapperTable(names);
                    }

                    var values = new object[effectiveFieldCount];

                    if (returnNullIfFirstMissing)
                    {
                        values[0] = r.GetValue(startBound);
                        if (values[0] is DBNull)
                        {
                            return null;
                        }
                    }

                    if (startBound == 0)
                    {
                        for (int i = 0; i < values.Length; i++)
                        {
                            object val = r.GetValue(i);
                            values[i] = val is DBNull ? null : val;
                        }
                    }
                    else
                    {
                        var begin = returnNullIfFirstMissing ? 1 : 0;
                        for (var iter = begin; iter < effectiveFieldCount; ++iter)
                        {
                            object obj = r.GetValue(iter + startBound);
                            values[iter] = obj is DBNull ? null : obj;
                        }
                    }
                    return new DapperRow(table, values);
                };
        }
#else
        internal static Func<IDataReader, object> GetDictionaryDeserializer(IDataRecord reader, int startBound, int length, bool returnNullIfFirstMissing)
        {
            var fieldCount = reader.FieldCount;
            if (length == -1)
            {
                length = fieldCount - startBound;
            }

            if (fieldCount <= startBound)
            {
                throw MultiMapException(reader);
            }

            return
                 r =>
                 {
                     IDictionary<string, object> row = new Dictionary<string, object>(length);
                     for (var i = startBound; i < startBound + length; i++)
                     {
                         var tmp = r.GetValue(i);
                         tmp = tmp == DBNull.Value ? null : tmp;
                         row[r.GetName(i)] = tmp;
                         if (returnNullIfFirstMissing && i == startBound && tmp == null)
                         {
                             return null;
                         }
                     }
                     return row;
                 };
        }
#endif
        /// <summary>
        /// Internal use only
        /// </summary>
        /// <param name="value"></param>
        /// <returns></returns>
#if !DNXCORE50
        [Browsable(false)]
#endif
        [EditorBrowsable(EditorBrowsableState.Never)]
        [Obsolete("This method is for internal usage only", false)]
        public static char ReadChar(object value)
        {
            if (value == null || value is DBNull) throw new ArgumentNullException("value");
            string s = value as string;
            if (s == null || s.Length != 1) throw new ArgumentException("A single-character was expected", "value");
            return s[0];
        }

        /// <summary>
        /// Internal use only
        /// </summary>
#if !DNXCORE50
        [Browsable(false)]
#endif
        [EditorBrowsable(EditorBrowsableState.Never)]
        [Obsolete("This method is for internal usage only", false)]
        public static char? ReadNullableChar(object value)
        {
            if (value == null || value is DBNull) return null;
            string s = value as string;
            if (s == null || s.Length != 1) throw new ArgumentException("A single-character was expected", "value");
            return s[0];
        }


        /// <summary>
        /// Internal use only
        /// </summary>
#if !DNXCORE50
        [Browsable(false)]
#endif
        [EditorBrowsable(EditorBrowsableState.Never)]
        [Obsolete("This method is for internal usage only", true)]
        public static IDbDataParameter FindOrAddParameter(IDataParameterCollection parameters, IDbCommand command, string name)
        {
            IDbDataParameter result;
            if (parameters.Contains(name))
            {
                result = (IDbDataParameter)parameters[name];
            }
            else
            {
                result = command.CreateParameter();
                result.ParameterName = name;
                parameters.Add(result);
            }
            return result;
        }

        /// <summary>
        /// Internal use only
        /// </summary>
#if !DNXCORE50
        [Browsable(false)]
#endif
        [EditorBrowsable(EditorBrowsableState.Never)]
        [Obsolete("This method is for internal usage only", false)]
        public static void PackListParameters(IDbCommand command, string namePrefix, object value)
        {
            // initially we tried TVP, however it performs quite poorly.
            // keep in mind SQL support up to 2000 params easily in sp_executesql, needing more is rare

            if (FeatureSupport.Get(command.Connection).Arrays)
            {
                var arrayParm = command.CreateParameter();
                arrayParm.Value = SanitizeParameterValue(value);
                arrayParm.ParameterName = namePrefix;
                command.Parameters.Add(arrayParm);
            }
            else
            {
                var list = value as IEnumerable;
                var count = 0;
                bool isString = value is IEnumerable<string>;
                bool isDbString = value is IEnumerable<DbString>;
                foreach (var item in list)
                {
                    count++;
                    var listParam = command.CreateParameter();
                    listParam.ParameterName = namePrefix + count;
                    if (isString)
                    {
                        listParam.Size = DbString.DefaultLength;
                        if (item != null && ((string)item).Length > DbString.DefaultLength)
                        {
                            listParam.Size = -1;
                        }
                    }
                    if (isDbString && item as DbString != null)
                    {
                        var str = item as DbString;
                        str.AddParameter(command, listParam.ParameterName);
                    }
                    else
                    {
                        listParam.Value = SanitizeParameterValue(item);
                        command.Parameters.Add(listParam);
                    }
                }

                var regexIncludingUnknown = @"([?@:]" + Regex.Escape(namePrefix) + @")(?!\w)(\s+(?i)unknown(?-i))?";
                if (count == 0)
                {
                    command.CommandText = Regex.Replace(command.CommandText, regexIncludingUnknown, match =>
                    {
                        var variableName = match.Groups[1].Value;
                        if (match.Groups[2].Success)
                        {
                            // looks like an optimize hint; leave it alone!
                            return match.Value;
                        }
                        else
                        {
                            return "(SELECT " + variableName + " WHERE 1 = 0)";
                        }
                    }, RegexOptions.IgnoreCase | RegexOptions.Multiline | RegexOptions.CultureInvariant);                        
                    var dummyParam = command.CreateParameter();
                    dummyParam.ParameterName = namePrefix;
                    dummyParam.Value = DBNull.Value;
                    command.Parameters.Add(dummyParam);
                }
                else
                {
                    command.CommandText = Regex.Replace(command.CommandText, regexIncludingUnknown, match =>
                    {
                        var variableName = match.Groups[1].Value;
                        if (match.Groups[2].Success)
                        {
                            // looks like an optimize hint; expand it
                            var suffix = match.Groups[2].Value;
                                
                            var sb = GetStringBuilder().Append(variableName).Append(1).Append(suffix);
                            for (int i = 2; i <= count; i++)
                            {
                                sb.Append(',').Append(variableName).Append(i).Append(suffix);
                            }
                            return sb.__ToStringRecycle();
                        }
                        else
                        {
                            var sb = GetStringBuilder().Append('(').Append(variableName).Append(1);
                            for (int i = 2; i <= count; i++)
                            {
                                sb.Append(',').Append(variableName).Append(i);
                            }
                            return sb.Append(')').__ToStringRecycle();
                        }
                    }, RegexOptions.IgnoreCase | RegexOptions.Multiline | RegexOptions.CultureInvariant);
                }
            }

        }
        internal static object SanitizeParameterValue(object value)
        {
            if (value == null) return DBNull.Value;
            if (value is Enum)
            {
                TypeCode typeCode;
                if (value is IConvertible)
                {
                    typeCode = ((IConvertible)value).GetTypeCode();
                }
                else
                {
                    typeCode = TypeExtensions.GetTypeCode(Enum.GetUnderlyingType(value.GetType()));
                }
                switch (typeCode)
                {
                    case TypeCode.Byte: return (byte)value;
                    case TypeCode.SByte: return (sbyte)value;
                    case TypeCode.Int16: return (short)value;
                    case TypeCode.Int32: return (int)value;
                    case TypeCode.Int64: return (long)value;
                    case TypeCode.UInt16: return (ushort)value;
                    case TypeCode.UInt32: return (uint)value;
                    case TypeCode.UInt64: return (ulong)value;
                }
            }
            return value;
        }
        private static IEnumerable<PropertyInfo> FilterParameters(IEnumerable<PropertyInfo> parameters, string sql)
        {
            return parameters.Where(p => Regex.IsMatch(sql, @"[?@:]" + p.Name + "([^a-z0-9_]+|$)", RegexOptions.IgnoreCase | RegexOptions.Multiline | RegexOptions.CultureInvariant));
        }

        // look for ? / @ / : *by itself*
        static readonly Regex smellsLikeOleDb = new Regex(@"(?<![a-z0-9@_])[?@:](?![a-z0-9@_])", RegexOptions.IgnoreCase | RegexOptions.Multiline | RegexOptions.CultureInvariant | RegexOptions.Compiled),
            literalTokens = new Regex(@"(?<![a-z0-9_])\{=([a-z0-9_]+)\}", RegexOptions.IgnoreCase | RegexOptions.Multiline | RegexOptions.CultureInvariant | RegexOptions.Compiled),
            pseudoPositional = new Regex(@"\?([a-z_][a-z0-9_]*)\?", RegexOptions.IgnoreCase | RegexOptions.CultureInvariant | RegexOptions.Compiled);

        /// <summary>
        /// Represents a placeholder for a value that should be replaced as a literal value in the resulting sql
        /// </summary>
        internal struct LiteralToken
        {
            private readonly string token, member;
            /// <summary>
            /// The text in the original command that should be replaced
            /// </summary>
            public string Token { get { return token; } }

            /// <summary>
            /// The name of the member referred to by the token
            /// </summary>
            public string Member { get { return member; } }
            internal LiteralToken(string token, string member)
            {
                this.token = token;
                this.member = member;
            }

            internal static readonly IList<LiteralToken> None = new LiteralToken[0];
        }

        /// <summary>
        /// Replace all literal tokens with their text form
        /// </summary>
        public static void ReplaceLiterals(this IParameterLookup parameters, IDbCommand command)
        {
            var tokens = GetLiteralTokens(command.CommandText);
            if (tokens.Count != 0) ReplaceLiterals(parameters, command, tokens);
        }

        internal static readonly MethodInfo format = typeof(SqlMapper).GetMethod("Format", BindingFlags.Public | BindingFlags.Static);
        /// <summary>
        /// Convert numeric values to their string form for SQL literal purposes
        /// </summary>
        [Obsolete("This is intended for internal usage only")]
        public static string Format(object value)
        {
            if (value == null)
            {
                return "null";
            }
            else
            {
                switch (TypeExtensions.GetTypeCode(value.GetType()))
                {
#if !DNXCORE50
                    case TypeCode.DBNull:
                        return "null";
#endif
                    case TypeCode.Boolean:
                        return ((bool)value) ? "1" : "0";
                    case TypeCode.Byte:
                        return ((byte)value).ToString(CultureInfo.InvariantCulture);
                    case TypeCode.SByte:
                        return ((sbyte)value).ToString(CultureInfo.InvariantCulture);
                    case TypeCode.UInt16:
                        return ((ushort)value).ToString(CultureInfo.InvariantCulture);
                    case TypeCode.Int16:
                        return ((short)value).ToString(CultureInfo.InvariantCulture);
                    case TypeCode.UInt32:
                        return ((uint)value).ToString(CultureInfo.InvariantCulture);
                    case TypeCode.Int32:
                        return ((int)value).ToString(CultureInfo.InvariantCulture);
                    case TypeCode.UInt64:
                        return ((ulong)value).ToString(CultureInfo.InvariantCulture);
                    case TypeCode.Int64:
                        return ((long)value).ToString(CultureInfo.InvariantCulture);
                    case TypeCode.Single:
                        return ((float)value).ToString(CultureInfo.InvariantCulture);
                    case TypeCode.Double:
                        return ((double)value).ToString(CultureInfo.InvariantCulture);
                    case TypeCode.Decimal:
                        return ((decimal)value).ToString(CultureInfo.InvariantCulture);
                    default:
                        var multiExec = GetMultiExec(value);
                        if(multiExec != null)
                        {
                            StringBuilder sb = null;
                            bool first = true;
                            foreach (object subval in multiExec)
                            {
                                if(first)
                                {
                                    sb = GetStringBuilder().Append('(');
                                    first = false;
                                }
                                else
                                {
                                    sb.Append(',');
                                }
                                sb.Append(Format(subval));
                            }
                            if(first)
                            {
                                return "(select null where 1=0)";
                            }
                            else
                            {
                                return sb.Append(')').__ToStringRecycle();
                            }
                        }
                        throw new NotSupportedException(value.GetType().Name);
                }
            }
        }


        internal static void ReplaceLiterals(IParameterLookup parameters, IDbCommand command, IList<LiteralToken> tokens)
        {
            var sql = command.CommandText;
            foreach (var token in tokens)
            {
                object value = parameters[token.Member];
#pragma warning disable 0618
                string text = Format(value);
#pragma warning restore 0618
                sql = sql.Replace(token.Token, text);
            }
            command.CommandText = sql;
        }

        internal static IList<LiteralToken> GetLiteralTokens(string sql)
        {
            if (string.IsNullOrEmpty(sql)) return LiteralToken.None;
            if (!literalTokens.IsMatch(sql)) return LiteralToken.None;

            var matches = literalTokens.Matches(sql);
            var found = new HashSet<string>(StringComparer.Ordinal);
            List<LiteralToken> list = new List<LiteralToken>(matches.Count);
            foreach(Match match in matches)
            {
                string token = match.Value;
                if(found.Add(match.Value))
                {
                    list.Add(new LiteralToken(token, match.Groups[1].Value));
                }
            }
            return list.Count == 0 ? LiteralToken.None : list;
        }

        /// <summary>
        /// Internal use only
        /// </summary>
        public static Action<IDbCommand, object> CreateParamInfoGenerator(Identity identity, bool checkForDuplicates, bool removeUnused)
        {
            return CreateParamInfoGenerator(identity, checkForDuplicates, removeUnused, GetLiteralTokens(identity.sql));
        }

        internal static Action<IDbCommand, object> CreateParamInfoGenerator(Identity identity, bool checkForDuplicates, bool removeUnused, IList<LiteralToken> literals)
        {
            Type type = identity.parametersType;
            
            bool filterParams = false;
            if (removeUnused && identity.commandType.GetValueOrDefault(CommandType.Text) == CommandType.Text)
            {
                filterParams = !smellsLikeOleDb.IsMatch(identity.sql);
            }
            var dm = new DynamicMethod(string.Format("ParamInfo{0}", Guid.NewGuid()), null, new[] { typeof(IDbCommand), typeof(object) }, type, true);

            var il = dm.GetILGenerator();

            bool isStruct = type.IsValueType();
            bool haveInt32Arg1 = false;
            il.Emit(OpCodes.Ldarg_1); // stack is now [untyped-param]
            if (isStruct)
            {
                il.DeclareLocal(type.MakePointerType());
                il.Emit(OpCodes.Unbox, type); // stack is now [typed-param]
            }
            else
            {
                il.DeclareLocal(type); // 0
                il.Emit(OpCodes.Castclass, type); // stack is now [typed-param]
            }
            il.Emit(OpCodes.Stloc_0);// stack is now empty

            il.Emit(OpCodes.Ldarg_0); // stack is now [command]
            il.EmitCall(OpCodes.Callvirt, typeof(IDbCommand).GetProperty("Parameters").GetGetMethod(), null); // stack is now [parameters]

            var propsArr = type.GetProperties().Where(p => p.GetIndexParameters().Length == 0).ToArray();
            var ctors = type.GetConstructors();
            ParameterInfo[] ctorParams;
            IEnumerable<PropertyInfo> props = null;
            // try to detect tuple patterns, e.g. anon-types, and use that to choose the order
            // otherwise: alphabetical
            if (ctors.Length == 1 && propsArr.Length == (ctorParams = ctors[0].GetParameters()).Length)
            {
                // check if reflection was kind enough to put everything in the right order for us
                bool ok = true;
                for (int i = 0; i < propsArr.Length; i++)
                {
                    if (!string.Equals(propsArr[i].Name, ctorParams[i].Name, StringComparison.OrdinalIgnoreCase))
                    {
                        ok = false;
                        break;
                    }
                }
                if(ok)
                {
                    // pre-sorted; the reflection gods have smiled upon us
                    props = propsArr;
                }
                else { // might still all be accounted for; check the hard way
                    var positionByName = new Dictionary<string,int>(StringComparer.OrdinalIgnoreCase);
                    foreach(var param in ctorParams)
                    {
                        positionByName[param.Name] = param.Position;
                    }
                    if (positionByName.Count == propsArr.Length)
                    {
                        int[] positions = new int[propsArr.Length];
                        ok = true;
                        for (int i = 0; i < propsArr.Length; i++)
                        {
                            int pos;
                            if (!positionByName.TryGetValue(propsArr[i].Name, out pos))
                            {
                                ok = false;
                                break;
                            }
                            positions[i] = pos;
                        }
                        if (ok)
                        {
                            Array.Sort(positions, propsArr);
                            props = propsArr;
                        }
                    }
                }
            }
            if(props == null) props = propsArr.OrderBy(x => x.Name);
            if (filterParams)
            {
                props = FilterParameters(props, identity.sql);
            }

            var callOpCode = isStruct ? OpCodes.Call : OpCodes.Callvirt;
            foreach (var prop in props)
            {
                if (typeof(ICustomQueryParameter).IsAssignableFrom(prop.PropertyType))
                {
                    il.Emit(OpCodes.Ldloc_0); // stack is now [parameters] [typed-param]
                    il.Emit(callOpCode, prop.GetGetMethod()); // stack is [parameters] [custom]
                    il.Emit(OpCodes.Ldarg_0); // stack is now [parameters] [custom] [command]
                    il.Emit(OpCodes.Ldstr, prop.Name); // stack is now [parameters] [custom] [command] [name]
                    il.EmitCall(OpCodes.Callvirt, prop.PropertyType.GetMethod("AddParameter"), null); // stack is now [parameters]
                    continue;
                }
                ITypeHandler handler;
                DbType dbType = LookupDbType(prop.PropertyType, prop.Name, true, out handler);
                if (dbType == DynamicParameters.EnumerableMultiParameter)
                {
                    // this actually represents special handling for list types;
                    il.Emit(OpCodes.Ldarg_0); // stack is now [parameters] [command]
                    il.Emit(OpCodes.Ldstr, prop.Name); // stack is now [parameters] [command] [name]
                    il.Emit(OpCodes.Ldloc_0); // stack is now [parameters] [command] [name] [typed-param]
                    il.Emit(callOpCode, prop.GetGetMethod()); // stack is [parameters] [command] [name] [typed-value]
                    if (prop.PropertyType.IsValueType())
                    {
                        il.Emit(OpCodes.Box, prop.PropertyType); // stack is [parameters] [command] [name] [boxed-value]
                    }
                    il.EmitCall(OpCodes.Call, typeof(SqlMapper).GetMethod("PackListParameters"), null); // stack is [parameters]
                    continue;
                }
                il.Emit(OpCodes.Dup); // stack is now [parameters] [parameters]

                il.Emit(OpCodes.Ldarg_0); // stack is now [parameters] [parameters] [command]

                if (checkForDuplicates)
                {
                    // need to be a little careful about adding; use a utility method
                    il.Emit(OpCodes.Ldstr, prop.Name); // stack is now [parameters] [parameters] [command] [name]
                    il.EmitCall(OpCodes.Call, typeof(SqlMapper).GetMethod("FindOrAddParameter"), null); // stack is [parameters] [parameter]
                }
                else
                {
                    // no risk of duplicates; just blindly add
                    il.EmitCall(OpCodes.Callvirt, typeof(IDbCommand).GetMethod("CreateParameter"), null);// stack is now [parameters] [parameters] [parameter]

                    il.Emit(OpCodes.Dup);// stack is now [parameters] [parameters] [parameter] [parameter]
                    il.Emit(OpCodes.Ldstr, prop.Name); // stack is now [parameters] [parameters] [parameter] [parameter] [name]
                    il.EmitCall(OpCodes.Callvirt, typeof(IDataParameter).GetProperty("ParameterName").GetSetMethod(), null);// stack is now [parameters] [parameters] [parameter]
                }
                if (dbType != DbType.Time && handler == null) // https://connect.microsoft.com/VisualStudio/feedback/details/381934/sqlparameter-dbtype-dbtype-time-sets-the-parameter-to-sqldbtype-datetime-instead-of-sqldbtype-time
                {
                    il.Emit(OpCodes.Dup);// stack is now [parameters] [[parameters]] [parameter] [parameter]
                    if (dbType == DbType.Object && prop.PropertyType == typeof(object)) // includes dynamic
                    {
                        // look it up from the param value
                        il.Emit(OpCodes.Ldloc_0); // stack is now [parameters] [[parameters]] [parameter] [parameter] [typed-param]
                        il.Emit(callOpCode, prop.GetGetMethod()); // stack is [parameters] [[parameters]] [parameter] [parameter] [object-value]
                        il.Emit(OpCodes.Call, typeof(SqlMapper).GetMethod("GetDbType", BindingFlags.Static | BindingFlags.Public)); // stack is now [parameters] [[parameters]] [parameter] [parameter] [db-type]
                    }
                    else
                    {
                        // constant value; nice and simple
                        EmitInt32(il, (int)dbType);// stack is now [parameters] [[parameters]] [parameter] [parameter] [db-type]
                    }
                    il.EmitCall(OpCodes.Callvirt, typeof(IDataParameter).GetProperty("DbType").GetSetMethod(), null);// stack is now [parameters] [[parameters]] [parameter]
                }

                il.Emit(OpCodes.Dup);// stack is now [parameters] [[parameters]] [parameter] [parameter]
                EmitInt32(il, (int)ParameterDirection.Input);// stack is now [parameters] [[parameters]] [parameter] [parameter] [dir]
                il.EmitCall(OpCodes.Callvirt, typeof(IDataParameter).GetProperty("Direction").GetSetMethod(), null);// stack is now [parameters] [[parameters]] [parameter]

                il.Emit(OpCodes.Dup);// stack is now [parameters] [[parameters]] [parameter] [parameter]
                il.Emit(OpCodes.Ldloc_0); // stack is now [parameters] [[parameters]] [parameter] [parameter] [typed-param]
                il.Emit(callOpCode, prop.GetGetMethod()); // stack is [parameters] [[parameters]] [parameter] [parameter] [typed-value]
                bool checkForNull = true;
                if (prop.PropertyType.IsValueType())
                {
                    il.Emit(OpCodes.Box, prop.PropertyType); // stack is [parameters] [[parameters]] [parameter] [parameter] [boxed-value]
                    if (Nullable.GetUnderlyingType(prop.PropertyType) == null)
                    {   // struct but not Nullable<T>; boxed value cannot be null
                        checkForNull = false;
                    }
                }
                if (checkForNull)
                {
                    if ((dbType == DbType.String || dbType == DbType.AnsiString) && !haveInt32Arg1)
                    {
                        il.DeclareLocal(typeof(int));
                        haveInt32Arg1 = true;
                    }
                    // relative stack: [boxed value]
                    il.Emit(OpCodes.Dup);// relative stack: [boxed value] [boxed value]
                    Label notNull = il.DefineLabel();
                    Label? allDone = (dbType == DbType.String || dbType == DbType.AnsiString) ? il.DefineLabel() : (Label?)null;
                    il.Emit(OpCodes.Brtrue_S, notNull);
                    // relative stack [boxed value = null]
                    il.Emit(OpCodes.Pop); // relative stack empty
                    il.Emit(OpCodes.Ldsfld, typeof(DBNull).GetField("Value")); // relative stack [DBNull]
                    if (dbType == DbType.String || dbType == DbType.AnsiString)
                    {
                        EmitInt32(il, 0);
                        il.Emit(OpCodes.Stloc_1);
                    }
                    if (allDone != null) il.Emit(OpCodes.Br_S, allDone.Value);
                    il.MarkLabel(notNull);
                    if (prop.PropertyType == typeof(string))
                    {
                        il.Emit(OpCodes.Dup); // [string] [string]
                        il.EmitCall(OpCodes.Callvirt, typeof(string).GetProperty("Length").GetGetMethod(), null); // [string] [length]
                        EmitInt32(il, DbString.DefaultLength); // [string] [length] [4000]
                        il.Emit(OpCodes.Cgt); // [string] [0 or 1]
                        Label isLong = il.DefineLabel(), lenDone = il.DefineLabel();
                        il.Emit(OpCodes.Brtrue_S, isLong);
                        EmitInt32(il, DbString.DefaultLength); // [string] [4000]
                        il.Emit(OpCodes.Br_S, lenDone);
                        il.MarkLabel(isLong);
                        EmitInt32(il, -1); // [string] [-1]
                        il.MarkLabel(lenDone);
                        il.Emit(OpCodes.Stloc_1); // [string] 
                    }
                    if (prop.PropertyType.FullName == LinqBinary)
                    {
                        il.EmitCall(OpCodes.Callvirt, prop.PropertyType.GetMethod("ToArray", BindingFlags.Public | BindingFlags.Instance), null);
                    }
                    if (allDone != null) il.MarkLabel(allDone.Value);
                    // relative stack [boxed value or DBNull]
                }

                if (handler != null)
                {
#pragma warning disable 618
                    il.Emit(OpCodes.Call, typeof(TypeHandlerCache<>).MakeGenericType(prop.PropertyType).GetMethod("SetValue")); // stack is now [parameters] [[parameters]] [parameter]
#pragma warning restore 618
                }
                else
                {
                    il.EmitCall(OpCodes.Callvirt, typeof(IDataParameter).GetProperty("Value").GetSetMethod(), null);// stack is now [parameters] [[parameters]] [parameter]
                }

                if (prop.PropertyType == typeof(string))
                {
                    var endOfSize = il.DefineLabel();
                    // don't set if 0
                    il.Emit(OpCodes.Ldloc_1); // [parameters] [[parameters]] [parameter] [size]
                    il.Emit(OpCodes.Brfalse_S, endOfSize); // [parameters] [[parameters]] [parameter]

                    il.Emit(OpCodes.Dup);// stack is now [parameters] [[parameters]] [parameter] [parameter]
                    il.Emit(OpCodes.Ldloc_1); // stack is now [parameters] [[parameters]] [parameter] [parameter] [size]
                    il.EmitCall(OpCodes.Callvirt, typeof(IDbDataParameter).GetProperty("Size").GetSetMethod(), null); // stack is now [parameters] [[parameters]] [parameter]

                    il.MarkLabel(endOfSize);
                }
                if (checkForDuplicates)
                {
                    // stack is now [parameters] [parameter]
                    il.Emit(OpCodes.Pop); // don't need parameter any more
                }
                else
                {
                    // stack is now [parameters] [parameters] [parameter]
                    // blindly add
                    il.EmitCall(OpCodes.Callvirt, typeof(IList).GetMethod("Add"), null); // stack is now [parameters]
                    il.Emit(OpCodes.Pop); // IList.Add returns the new index (int); we don't care
                }
            }

            // stack is currently [parameters]
            il.Emit(OpCodes.Pop); // stack is now empty

            if(literals.Count != 0 && propsArr != null)
            {
                il.Emit(OpCodes.Ldarg_0); // command
                il.Emit(OpCodes.Ldarg_0); // command, command
                var cmdText = typeof(IDbCommand).GetProperty("CommandText");
                il.EmitCall(OpCodes.Callvirt, cmdText.GetGetMethod(), null); // command, sql
                Dictionary<Type, LocalBuilder> locals = null;
                LocalBuilder local = null;
                foreach (var literal in literals)
                {
                    // find the best member, preferring case-sensitive
                    PropertyInfo exact = null, fallback = null;
                    string huntName = literal.Member;
                    for(int i = 0; i < propsArr.Length;i++)
                    {
                        string thisName = propsArr[i].Name;
                        if(string.Equals(thisName, huntName, StringComparison.OrdinalIgnoreCase))
                        {
                            fallback = propsArr[i];
                            if(string.Equals(thisName, huntName, StringComparison.Ordinal))
                            {
                                exact = fallback;
                                break;
                            }
                        }
                    }
                    var prop = exact ?? fallback;

                    if(prop != null)
                    {
                        il.Emit(OpCodes.Ldstr, literal.Token);
                        il.Emit(OpCodes.Ldloc_0); // command, sql, typed parameter
                        il.EmitCall(callOpCode, prop.GetGetMethod(), null); // command, sql, typed value
                        Type propType = prop.PropertyType;
                        var typeCode = TypeExtensions.GetTypeCode(propType);
                        switch (typeCode)
                        {
                            case TypeCode.Boolean:
                                Label ifTrue = il.DefineLabel(), allDone = il.DefineLabel();
                                il.Emit(OpCodes.Brtrue_S, ifTrue);
                                il.Emit(OpCodes.Ldstr, "0");
                                il.Emit(OpCodes.Br_S, allDone);
                                il.MarkLabel(ifTrue);
                                il.Emit(OpCodes.Ldstr, "1");
                                il.MarkLabel(allDone);
                                break;
                            case TypeCode.Byte:
                            case TypeCode.SByte:
                            case TypeCode.UInt16:
                            case TypeCode.Int16:
                            case TypeCode.UInt32:
                            case TypeCode.Int32:
                            case TypeCode.UInt64:
                            case TypeCode.Int64:
                            case TypeCode.Single:
                            case TypeCode.Double:
                            case TypeCode.Decimal:
                                // need to stloc, ldloca, call
                                // re-use existing locals (both the last known, and via a dictionary)
                                var convert = GetToString(typeCode);
                                if (local == null || local.LocalType != propType)
                                {
                                    if (locals == null)
                                    {
                                        locals = new Dictionary<Type, LocalBuilder>();
                                        local = null;
                                    }
                                    else
                                    {
                                        if (!locals.TryGetValue(propType, out local)) local = null;
                                    }
                                    if (local == null)
                                    {
                                        local = il.DeclareLocal(propType);
                                        locals.Add(propType, local);
                                    }
                                }
                                il.Emit(OpCodes.Stloc, local); // command, sql
                                il.Emit(OpCodes.Ldloca, local); // command, sql, ref-to-value
                                il.EmitCall(OpCodes.Call, InvariantCulture, null); // command, sql, ref-to-value, culture
                                il.EmitCall(OpCodes.Call, convert, null); // command, sql, string value
                                break;
                            default:
                                if (propType.IsValueType()) il.Emit(OpCodes.Box, propType); // command, sql, object value
                                il.EmitCall(OpCodes.Call, format, null); // command, sql, string value
                                break;

                        }
                        il.EmitCall(OpCodes.Callvirt, StringReplace, null);
                    }
                }
                il.EmitCall(OpCodes.Callvirt, cmdText.GetSetMethod(), null); // empty
            }

            il.Emit(OpCodes.Ret);
            return (Action<IDbCommand, object>)dm.CreateDelegate(typeof(Action<IDbCommand, object>));
        }
        static readonly Dictionary<TypeCode, MethodInfo> toStrings = new[]
        {
            typeof(bool), typeof(sbyte), typeof(byte), typeof(ushort), typeof(short),
            typeof(uint), typeof(int), typeof(ulong), typeof(long), typeof(float), typeof(double), typeof(decimal)
        }.ToDictionary(x => TypeExtensions.GetTypeCode(x), x => x.GetPublicInstanceMethod("ToString", new[] { typeof(IFormatProvider) }));
        static MethodInfo GetToString(TypeCode typeCode)
        {
            MethodInfo method;
            return toStrings.TryGetValue(typeCode, out method) ? method : null;
        }
        static readonly MethodInfo StringReplace = typeof(string).GetPublicInstanceMethod("Replace", new Type[] { typeof(string), typeof(string) }),
            InvariantCulture = typeof(CultureInfo).GetProperty("InvariantCulture", BindingFlags.Public | BindingFlags.Static).GetGetMethod();

        private static int ExecuteCommand(IDbConnection cnn, ref CommandDefinition command, Action<IDbCommand, object> paramReader)
        {
            IDbCommand cmd = null;
            bool wasClosed = cnn.State == ConnectionState.Closed;
            try
            {
                cmd = command.SetupCommand(cnn, paramReader);
                if (wasClosed) cnn.Open();
                int result = cmd.ExecuteNonQuery();
                command.OnCompleted();
                return result;
            }
            finally
            {
                if (wasClosed) cnn.Close();
                if (cmd != null) cmd.Dispose();
            }
        }

        private static T ExecuteScalarImpl<T>(IDbConnection cnn, ref CommandDefinition command)
        {
            Action<IDbCommand, object> paramReader = null;
            object param = command.Parameters;
            if (param != null)
            {
                var identity = new Identity(command.CommandText, command.CommandType, cnn, null, param.GetType(), null);
                paramReader = GetCacheInfo(identity, command.Parameters, command.AddToCache).ParamReader;
            }

            IDbCommand cmd = null;
            bool wasClosed = cnn.State == ConnectionState.Closed;
            object result;
            try
            {
                cmd = command.SetupCommand(cnn, paramReader);
                if (wasClosed) cnn.Open();
                result =cmd.ExecuteScalar();
                command.OnCompleted();
            }
            finally
            {
                if (wasClosed) cnn.Close();
                if (cmd != null) cmd.Dispose();
            }
            return Parse<T>(result);
        }

        private static IDataReader ExecuteReaderImpl(IDbConnection cnn, ref CommandDefinition command, CommandBehavior commandBehavior, out IDbCommand cmd)
        {
            Action<IDbCommand, object> paramReader = GetParameterReader(cnn, ref command);
            cmd = null;
            bool wasClosed = cnn.State == ConnectionState.Closed, disposeCommand = true;
            try
            {
                cmd = command.SetupCommand(cnn, paramReader);
                if (wasClosed) cnn.Open();
                if (wasClosed) commandBehavior |= CommandBehavior.CloseConnection;
                var reader = cmd.ExecuteReader(commandBehavior);
                wasClosed = false; // don't dispose before giving it to them!
                disposeCommand = false;
                // note: command.FireOutputCallbacks(); would be useless here; parameters come at the **end** of the TDS stream
                return reader;
            }
            finally
            {
                if (wasClosed) cnn.Close();
                if (cmd != null && disposeCommand) cmd.Dispose();
            }
        }

        private static Action<IDbCommand, object> GetParameterReader(IDbConnection cnn, ref CommandDefinition command)
        {
            object param = command.Parameters;
            IEnumerable multiExec = GetMultiExec(param);
            Identity identity;
            CacheInfo info = null;
            if (multiExec != null)
            {
                throw new NotSupportedException("MultiExec is not supported by ExecuteReader");
            }

            // nice and simple
            if (param != null)
            {
                identity = new Identity(command.CommandText, command.CommandType, cnn, null, param.GetType(), null);
                info = GetCacheInfo(identity, param, command.AddToCache);
            }
            var paramReader = info == null ? null : info.ParamReader;
            return paramReader;
        }

        private static Func<IDataReader, object> GetStructDeserializer(Type type, Type effectiveType, int index)
        {
            // no point using special per-type handling here; it boils down to the same, plus not all are supported anyway (see: SqlDataReader.GetChar - not supported!)
#pragma warning disable 618
            if (type == typeof(char))
            { // this *does* need special handling, though
                return r => SqlMapper.ReadChar(r.GetValue(index));
            }
            if (type == typeof(char?))
            {
                return r => SqlMapper.ReadNullableChar(r.GetValue(index));
            }
            if (type.FullName == LinqBinary)
            {
                return r => Activator.CreateInstance(type, r.GetValue(index));
            }
#pragma warning restore 618

            if (effectiveType.IsEnum())
            {   // assume the value is returned as the correct type (int/byte/etc), but box back to the typed enum
                return r =>
                {
                    var val = r.GetValue(index);
                    if(val is float || val is double || val is decimal)
                    {
                        val = Convert.ChangeType(val, Enum.GetUnderlyingType(effectiveType), CultureInfo.InvariantCulture);
                    }
                    return val is DBNull ? null : Enum.ToObject(effectiveType, val);
                };
            }
            ITypeHandler handler;
            if(typeHandlers.TryGetValue(type, out handler))
            {
                return r =>
                {
                    var val = r.GetValue(index);
                    return val is DBNull ? null : handler.Parse(type, val);
                };
            }
            return r =>
            {
                var val = r.GetValue(index);
                return val is DBNull ? null : val;
            };
        }

        private static T Parse<T>(object value)
        {
            if (value == null || value is DBNull) return default(T);
            if (value is T) return (T)value;
            var type = typeof(T);
            type = Nullable.GetUnderlyingType(type) ?? type;
            if (type.IsEnum())
            {
                if (value is float || value is double || value is decimal)
                {
                    value = Convert.ChangeType(value, Enum.GetUnderlyingType(type), CultureInfo.InvariantCulture);
                }
                return (T)Enum.ToObject(type, value);
            }
            ITypeHandler handler;
            if (typeHandlers.TryGetValue(type, out handler))
            {
                return (T)handler.Parse(type, value);
            }
            return (T)Convert.ChangeType(value, type, CultureInfo.InvariantCulture);
        }

        static readonly MethodInfo
                    enumParse = typeof(Enum).GetMethod("Parse", new Type[] { typeof(Type), typeof(string), typeof(bool) }),
                    getItem = typeof(IDataRecord).GetProperties(BindingFlags.Instance | BindingFlags.Public)
                        .Where(p => p.GetIndexParameters().Any() && p.GetIndexParameters()[0].ParameterType == typeof(int))
                        .Select(p => p.GetGetMethod()).First();

        /// <summary>
        /// Gets type-map for the given type
        /// </summary>
        /// <returns>Type map implementation, DefaultTypeMap instance if no override present</returns>
        public static ITypeMap GetTypeMap(Type type)
        {
            if (type == null) throw new ArgumentNullException("type");
#if DNXCORE50
            ITypeMap map = null;
#else
            var map = (ITypeMap)_typeMaps[type];
#endif
            if (map == null)
            {
                lock (_typeMaps)
                {   // double-checked; store this to avoid reflection next time we see this type
                    // since multiple queries commonly use the same domain-entity/DTO/view-model type
#if DNXCORE50
                    if (!_typeMaps.TryGetValue(type, out map)) map = null;
#else
                    map = (ITypeMap)_typeMaps[type];
#endif

                        if (map == null)
                    {
                        map = new DefaultTypeMap(type);
                        _typeMaps[type] = map;
                    }
                }
            }
            return map;
        }

        // use Hashtable to get free lockless reading
#if DNXCORE50
        private static readonly Dictionary<Type,ITypeMap> _typeMaps = new Dictionary<Type, ITypeMap>();
#else
        private static readonly Hashtable _typeMaps = new Hashtable();
#endif

        /// <summary>
        /// Set custom mapping for type deserializers
        /// </summary>
        /// <param name="type">Entity type to override</param>
        /// <param name="map">Mapping rules impementation, null to remove custom map</param>
        public static void SetTypeMap(Type type, ITypeMap map)
        {
            if (type == null)
                throw new ArgumentNullException("type");

            if (map == null || map is DefaultTypeMap)
            {
                lock (_typeMaps)
                {
                    _typeMaps.Remove(type);
                }
            }
            else
            {
                lock (_typeMaps)
                {
                    _typeMaps[type] = map;
                }
            }

            PurgeQueryCacheByType(type);
        }

        /// <summary>
        /// Internal use only
        /// </summary>
        /// <param name="type"></param>
        /// <param name="reader"></param>
        /// <param name="startBound"></param>
        /// <param name="length"></param>
        /// <param name="returnNullIfFirstMissing"></param>
        /// <returns></returns>
        public static Func<IDataReader, object> GetTypeDeserializer(
#if CSHARP30
Type type, IDataReader reader, int startBound, int length, bool returnNullIfFirstMissing
#else
Type type, IDataReader reader, int startBound = 0, int length = -1, bool returnNullIfFirstMissing = false
#endif
)
        {

            var dm = new DynamicMethod(string.Format("Deserialize{0}", Guid.NewGuid()), typeof(object), new[] { typeof(IDataReader) }, true);
            var il = dm.GetILGenerator();
            il.DeclareLocal(typeof(int));
            il.DeclareLocal(type);
            il.Emit(OpCodes.Ldc_I4_0);
            il.Emit(OpCodes.Stloc_0);

            if (length == -1)
            {
                length = reader.FieldCount - startBound;
            }

            if (reader.FieldCount <= startBound)
            {
                throw MultiMapException(reader);
            }

            var names = Enumerable.Range(startBound, length).Select(i => reader.GetName(i)).ToArray();

            ITypeMap typeMap = GetTypeMap(type);

            int index = startBound;

            ConstructorInfo specializedConstructor = null;

#if !DNXCORE50
            bool supportInitialize = false;
#endif
            if (type.IsValueType())
            {
                il.Emit(OpCodes.Ldloca_S, (byte)1);
                il.Emit(OpCodes.Initobj, type);
            }
            else
            {
                var types = new Type[length];
                for (int i = startBound; i < startBound + length; i++)
                {
                    types[i - startBound] = reader.GetFieldType(i);
                }

                var explicitConstr = typeMap.FindExplicitConstructor();
                if (explicitConstr != null)
                {
                    var structLocals = new Dictionary<Type, LocalBuilder>();

                    var consPs = explicitConstr.GetParameters();
                    foreach(var p in consPs)
                    {
                        if(!p.ParameterType.IsValueType())
                        {
                            il.Emit(OpCodes.Ldnull);
                        }
                        else
                        {
                            LocalBuilder loc;
                            if(!structLocals.TryGetValue(p.ParameterType, out loc))
                            {
                                structLocals[p.ParameterType] = loc = il.DeclareLocal(p.ParameterType);
                            }

                            il.Emit(OpCodes.Ldloca, (short)loc.LocalIndex);
                            il.Emit(OpCodes.Initobj, p.ParameterType);
                            il.Emit(OpCodes.Ldloca, (short)loc.LocalIndex);
                            il.Emit(OpCodes.Ldobj, p.ParameterType);
                        }
                    }

                    il.Emit(OpCodes.Newobj, explicitConstr);
                    il.Emit(OpCodes.Stloc_1);
#if !DNXCORE50
                    supportInitialize = typeof(ISupportInitialize).IsAssignableFrom(type);
                    if (supportInitialize)
                    {
                        il.Emit(OpCodes.Ldloc_1);
                        il.EmitCall(OpCodes.Callvirt, typeof(ISupportInitialize).GetMethod("BeginInit"), null);
                    }
#endif
                }
                else
                {
                    var ctor = typeMap.FindConstructor(names, types);
                    if (ctor == null)
                    {
                        string proposedTypes = "(" + string.Join(", ", types.Select((t, i) => t.FullName + " " + names[i]).ToArray()) + ")";
                        throw new InvalidOperationException(string.Format("A parameterless default constructor or one matching signature {0} is required for {1} materialization", proposedTypes, type.FullName));
                    }

                    if (ctor.GetParameters().Length == 0)
                    {
                        il.Emit(OpCodes.Newobj, ctor);
                        il.Emit(OpCodes.Stloc_1);
#if !DNXCORE50
                        supportInitialize = typeof(ISupportInitialize).IsAssignableFrom(type);
                        if (supportInitialize)
                        {
                            il.Emit(OpCodes.Ldloc_1);
                            il.EmitCall(OpCodes.Callvirt, typeof(ISupportInitialize).GetMethod("BeginInit"), null);
                        }
#endif
                    }
                    else
                    {
                        specializedConstructor = ctor;
                    }
                }
            }

            il.BeginExceptionBlock();
            if (type.IsValueType())
            {
                il.Emit(OpCodes.Ldloca_S, (byte)1);// [target]
            }
            else if (specializedConstructor == null)
            {
                il.Emit(OpCodes.Ldloc_1);// [target]
            }

            var members = (specializedConstructor != null
                ? names.Select(n => typeMap.GetConstructorParameter(specializedConstructor, n))
                : names.Select(n => typeMap.GetMember(n))).ToList();

            // stack is now [target]

            bool first = true;
            var allDone = il.DefineLabel();
            int enumDeclareLocal = -1, valueCopyLocal = il.DeclareLocal(typeof(object)).LocalIndex;
            foreach (var item in members)
            {
                if (item != null)
                {
                    if (specializedConstructor == null)
                        il.Emit(OpCodes.Dup); // stack is now [target][target]
                    Label isDbNullLabel = il.DefineLabel();
                    Label finishLabel = il.DefineLabel();

                    il.Emit(OpCodes.Ldarg_0); // stack is now [target][target][reader]
                    EmitInt32(il, index); // stack is now [target][target][reader][index]
                    il.Emit(OpCodes.Dup);// stack is now [target][target][reader][index][index]
                    il.Emit(OpCodes.Stloc_0);// stack is now [target][target][reader][index]
                    il.Emit(OpCodes.Callvirt, getItem); // stack is now [target][target][value-as-object]
                    il.Emit(OpCodes.Dup); // stack is now [target][target][value-as-object][value-as-object]
                    StoreLocal(il, valueCopyLocal);
                    Type colType = reader.GetFieldType(index);
                    Type memberType = item.MemberType;

                    if (memberType == typeof(char) || memberType == typeof(char?))
                    {
                        il.EmitCall(OpCodes.Call, typeof(SqlMapper).GetMethod(
                            memberType == typeof(char) ? "ReadChar" : "ReadNullableChar", BindingFlags.Static | BindingFlags.Public), null); // stack is now [target][target][typed-value]
                    }
                    else
                    {
                        il.Emit(OpCodes.Dup); // stack is now [target][target][value][value]
                        il.Emit(OpCodes.Isinst, typeof(DBNull)); // stack is now [target][target][value-as-object][DBNull or null]
                        il.Emit(OpCodes.Brtrue_S, isDbNullLabel); // stack is now [target][target][value-as-object]

                        // unbox nullable enums as the primitive, i.e. byte etc

                        var nullUnderlyingType = Nullable.GetUnderlyingType(memberType);
                        var unboxType = nullUnderlyingType != null && nullUnderlyingType.IsEnum() ? nullUnderlyingType : memberType;

                        if (unboxType.IsEnum())
                        {
                            Type numericType = Enum.GetUnderlyingType(unboxType);
                            if(colType == typeof(string))
                            {
                                if (enumDeclareLocal == -1)
                                {
                                    enumDeclareLocal = il.DeclareLocal(typeof(string)).LocalIndex;
                                }
                                il.Emit(OpCodes.Castclass, typeof(string)); // stack is now [target][target][string]
                                StoreLocal(il, enumDeclareLocal); // stack is now [target][target]
                                il.Emit(OpCodes.Ldtoken, unboxType); // stack is now [target][target][enum-type-token]
                                il.EmitCall(OpCodes.Call, typeof(Type).GetMethod("GetTypeFromHandle"), null);// stack is now [target][target][enum-type]
                                LoadLocal(il, enumDeclareLocal); // stack is now [target][target][enum-type][string]
                                il.Emit(OpCodes.Ldc_I4_1); // stack is now [target][target][enum-type][string][true]
                                il.EmitCall(OpCodes.Call, enumParse, null); // stack is now [target][target][enum-as-object]
                                il.Emit(OpCodes.Unbox_Any, unboxType); // stack is now [target][target][typed-value]
                            }
                            else
                            {
                                FlexibleConvertBoxedFromHeadOfStack(il, colType, unboxType, numericType);
                            }

                            if (nullUnderlyingType != null)
                            {
                                il.Emit(OpCodes.Newobj, memberType.GetConstructor(new[] { nullUnderlyingType })); // stack is now [target][target][typed-value]
                            }
                        }
                        else if (memberType.FullName == LinqBinary)
                        {
                            il.Emit(OpCodes.Unbox_Any, typeof(byte[])); // stack is now [target][target][byte-array]
                            il.Emit(OpCodes.Newobj, memberType.GetConstructor(new Type[] { typeof(byte[]) }));// stack is now [target][target][binary]
                        }
                        else
                        {
                            TypeCode dataTypeCode = TypeExtensions.GetTypeCode(colType), unboxTypeCode = TypeExtensions.GetTypeCode(unboxType);
                            bool hasTypeHandler;
                            if ((hasTypeHandler = typeHandlers.ContainsKey(unboxType)) || colType == unboxType || dataTypeCode == unboxTypeCode || dataTypeCode == TypeExtensions.GetTypeCode(nullUnderlyingType))
                            {
                                if (hasTypeHandler)
                                {
#pragma warning disable 618
                                    il.EmitCall(OpCodes.Call, typeof(TypeHandlerCache<>).MakeGenericType(unboxType).GetMethod("Parse"), null); // stack is now [target][target][typed-value]
#pragma warning restore 618
                                }
                                else
                                {
                                    il.Emit(OpCodes.Unbox_Any, unboxType); // stack is now [target][target][typed-value]
                                }
                            }
                            else
                            {
                                // not a direct match; need to tweak the unbox
                                FlexibleConvertBoxedFromHeadOfStack(il, colType, nullUnderlyingType ?? unboxType, null);
                                if (nullUnderlyingType != null)
                                {
                                    il.Emit(OpCodes.Newobj, unboxType.GetConstructor(new[] { nullUnderlyingType })); // stack is now [target][target][typed-value]
                                }

                            }

                        }
                    }
                    if (specializedConstructor == null)
                    {
                        // Store the value in the property/field
                        if (item.Property != null)
                        {
                            if (type.IsValueType())
                            {
                                il.Emit(OpCodes.Call, DefaultTypeMap.GetPropertySetter(item.Property, type)); // stack is now [target]
                            }
                            else
                            {
                                il.Emit(OpCodes.Callvirt, DefaultTypeMap.GetPropertySetter(item.Property, type)); // stack is now [target]
                            }
                        }
                        else
                        {
                            il.Emit(OpCodes.Stfld, item.Field); // stack is now [target]
                        }
                    }

                    il.Emit(OpCodes.Br_S, finishLabel); // stack is now [target]

                    il.MarkLabel(isDbNullLabel); // incoming stack: [target][target][value]
                    if (specializedConstructor != null)
                    {
                        il.Emit(OpCodes.Pop);
                        if (item.MemberType.IsValueType())
                        {
                            int localIndex = il.DeclareLocal(item.MemberType).LocalIndex;
                            LoadLocalAddress(il, localIndex);
                            il.Emit(OpCodes.Initobj, item.MemberType);
                            LoadLocal(il, localIndex);
                        }
                        else
                        {
                            il.Emit(OpCodes.Ldnull);
                        }
                    }
                    else
                    {
                        il.Emit(OpCodes.Pop); // stack is now [target][target]
                        il.Emit(OpCodes.Pop); // stack is now [target]
                    }

                    if (first && returnNullIfFirstMissing)
                    {
                        il.Emit(OpCodes.Pop);
                        il.Emit(OpCodes.Ldnull); // stack is now [null]
                        il.Emit(OpCodes.Stloc_1);
                        il.Emit(OpCodes.Br, allDone);
                    }

                    il.MarkLabel(finishLabel);
                }
                first = false;
                index += 1;
            }
            if (type.IsValueType())
            {
                il.Emit(OpCodes.Pop);
            }
            else
            {
                if (specializedConstructor != null)
                {
                    il.Emit(OpCodes.Newobj, specializedConstructor);
                }
                il.Emit(OpCodes.Stloc_1); // stack is empty
#if !DNXCORE50
                if (supportInitialize)
                {
                    il.Emit(OpCodes.Ldloc_1);
                    il.EmitCall(OpCodes.Callvirt, typeof(ISupportInitialize).GetMethod("EndInit"), null);
                }
#endif
            }
            il.MarkLabel(allDone);
            il.BeginCatchBlock(typeof(Exception)); // stack is Exception
            il.Emit(OpCodes.Ldloc_0); // stack is Exception, index
            il.Emit(OpCodes.Ldarg_0); // stack is Exception, index, reader
            LoadLocal(il, valueCopyLocal); // stack is Exception, index, reader, value
            il.EmitCall(OpCodes.Call, typeof(SqlMapper).GetMethod("ThrowDataException"), null);
            il.EndExceptionBlock();

            il.Emit(OpCodes.Ldloc_1); // stack is [rval]
            if (type.IsValueType())
            {
                il.Emit(OpCodes.Box, type);
            }
            il.Emit(OpCodes.Ret);

            return (Func<IDataReader, object>)dm.CreateDelegate(typeof(Func<IDataReader, object>));
        }

        private static void FlexibleConvertBoxedFromHeadOfStack(ILGenerator il, Type from, Type to, Type via)
        {
            MethodInfo op;
            if(from == (via ?? to))
            {
                il.Emit(OpCodes.Unbox_Any, to); // stack is now [target][target][typed-value]
            }
            else if ((op = GetOperator(from,to)) != null)
            {
                // this is handy for things like decimal <===> double
                il.Emit(OpCodes.Unbox_Any, from); // stack is now [target][target][data-typed-value]
                il.Emit(OpCodes.Call, op); // stack is now [target][target][typed-value]
            }
            else
            {
                bool handled = false;
                OpCode opCode = default(OpCode);
                switch (TypeExtensions.GetTypeCode(from))
                {
                    case TypeCode.Boolean:
                    case TypeCode.Byte:
                    case TypeCode.SByte:
                    case TypeCode.Int16:
                    case TypeCode.UInt16:
                    case TypeCode.Int32:
                    case TypeCode.UInt32:
                    case TypeCode.Int64:
                    case TypeCode.UInt64:
                    case TypeCode.Single:
                    case TypeCode.Double:
                        handled = true;
                        switch (TypeExtensions.GetTypeCode(via ?? to))
                        {
                            case TypeCode.Byte:
                                opCode = OpCodes.Conv_Ovf_I1_Un; break;
                            case TypeCode.SByte:
                                opCode = OpCodes.Conv_Ovf_I1; break;
                            case TypeCode.UInt16:
                                opCode = OpCodes.Conv_Ovf_I2_Un; break;
                            case TypeCode.Int16:
                                opCode = OpCodes.Conv_Ovf_I2; break;
                            case TypeCode.UInt32:
                                opCode = OpCodes.Conv_Ovf_I4_Un; break;
                            case TypeCode.Boolean: // boolean is basically an int, at least at this level
                            case TypeCode.Int32:
                                opCode = OpCodes.Conv_Ovf_I4; break;
                            case TypeCode.UInt64:
                                opCode = OpCodes.Conv_Ovf_I8_Un; break;
                            case TypeCode.Int64:
                                opCode = OpCodes.Conv_Ovf_I8; break;
                            case TypeCode.Single:
                                opCode = OpCodes.Conv_R4; break;
                            case TypeCode.Double:
                                opCode = OpCodes.Conv_R8; break;
                            default:
                                handled = false;
                                break;
                        }
                        break;
                }
                if (handled)
                {
                    il.Emit(OpCodes.Unbox_Any, from); // stack is now [target][target][col-typed-value]
                    il.Emit(opCode); // stack is now [target][target][typed-value]
                    if (to == typeof(bool))
                    { // compare to zero; I checked "csc" - this is the trick it uses; nice
                        il.Emit(OpCodes.Ldc_I4_0);
                        il.Emit(OpCodes.Ceq);
                        il.Emit(OpCodes.Ldc_I4_0);
                        il.Emit(OpCodes.Ceq);
                    }
                }
                else
                {
                    il.Emit(OpCodes.Ldtoken, via ?? to); // stack is now [target][target][value][member-type-token]
                    il.EmitCall(OpCodes.Call, typeof(Type).GetMethod("GetTypeFromHandle"), null); // stack is now [target][target][value][member-type]
                    il.EmitCall(OpCodes.Call, typeof(Convert).GetMethod("ChangeType", new Type[] { typeof(object), typeof(Type) }), null); // stack is now [target][target][boxed-member-type-value]
                    il.Emit(OpCodes.Unbox_Any, to); // stack is now [target][target][typed-value]
                }
            }            
        }

        static MethodInfo GetOperator(Type from, Type to)
        {
            if (to == null) return null;
            MethodInfo[] fromMethods, toMethods;
            return ResolveOperator(fromMethods = from.GetMethods(BindingFlags.Static | BindingFlags.Public), from, to, "op_Implicit")
                ?? ResolveOperator(toMethods = to.GetMethods(BindingFlags.Static | BindingFlags.Public), from, to, "op_Implicit")
                ?? ResolveOperator(fromMethods, from, to, "op_Explicit")
                ?? ResolveOperator(toMethods, from, to, "op_Explicit");

        }
        static MethodInfo ResolveOperator(MethodInfo[] methods, Type from, Type to, string name)
        {
            for (int i = 0; i < methods.Length; i++)
            {
                if (methods[i].Name != name || methods[i].ReturnType != to) continue;
                var args = methods[i].GetParameters();
                if (args.Length != 1 || args[0].ParameterType != from) continue;
                return methods[i];
            }
            return null;
        }

        private static void LoadLocal(ILGenerator il, int index)
        {
            if (index < 0 || index >= short.MaxValue) throw new ArgumentNullException("index");
            switch (index)
            {
                case 0: il.Emit(OpCodes.Ldloc_0); break;
                case 1: il.Emit(OpCodes.Ldloc_1); break;
                case 2: il.Emit(OpCodes.Ldloc_2); break;
                case 3: il.Emit(OpCodes.Ldloc_3); break;
                default:
                    if (index <= 255)
                    {
                        il.Emit(OpCodes.Ldloc_S, (byte)index);
                    }
                    else
                    {
                        il.Emit(OpCodes.Ldloc, (short)index);
                    }
                    break;
            }
        }
        private static void StoreLocal(ILGenerator il, int index)
        {
            if (index < 0 || index >= short.MaxValue) throw new ArgumentNullException("index");
            switch (index)
            {
                case 0: il.Emit(OpCodes.Stloc_0); break;
                case 1: il.Emit(OpCodes.Stloc_1); break;
                case 2: il.Emit(OpCodes.Stloc_2); break;
                case 3: il.Emit(OpCodes.Stloc_3); break;
                default:
                    if (index <= 255)
                    {
                        il.Emit(OpCodes.Stloc_S, (byte)index);
                    }
                    else
                    {
                        il.Emit(OpCodes.Stloc, (short)index);
                    }
                    break;
            }
        }
        private static void LoadLocalAddress(ILGenerator il, int index)
        {
            if (index < 0 || index >= short.MaxValue) throw new ArgumentNullException("index");

            if (index <= 255)
            {
                il.Emit(OpCodes.Ldloca_S, (byte)index);
            }
            else
            {
                il.Emit(OpCodes.Ldloca, (short)index);
            }
        }
        /// <summary>
        /// Throws a data exception, only used internally
        /// </summary>
        [Obsolete("Intended for internal use only")]
        public static void ThrowDataException(Exception ex, int index, IDataReader reader, object value)
        {
            Exception toThrow;
            try
            {
                string name = "(n/a)", formattedValue = "(n/a)";
                if (reader != null && index >= 0 && index < reader.FieldCount)
                {
                    name = reader.GetName(index);
                    try
                    {
                        if (value == null || value is DBNull)
                        {
                            formattedValue = "<null>";
                        }
                        else
                        {
                            formattedValue = Convert.ToString(value) + " - " + TypeExtensions.GetTypeCode(value.GetType());
                        }
                    }
                    catch (Exception valEx)
                    {
                        formattedValue = valEx.Message;
                    }
                }
                toThrow = new DataException(string.Format("Error parsing column {0} ({1}={2})", index, name, formattedValue), ex);
            }
            catch
            { // throw the **original** exception, wrapped as DataException
                toThrow = new DataException(ex.Message, ex);
            }
            throw toThrow;
        }
        private static void EmitInt32(ILGenerator il, int value)
        {
            switch (value)
            {
                case -1: il.Emit(OpCodes.Ldc_I4_M1); break;
                case 0: il.Emit(OpCodes.Ldc_I4_0); break;
                case 1: il.Emit(OpCodes.Ldc_I4_1); break;
                case 2: il.Emit(OpCodes.Ldc_I4_2); break;
                case 3: il.Emit(OpCodes.Ldc_I4_3); break;
                case 4: il.Emit(OpCodes.Ldc_I4_4); break;
                case 5: il.Emit(OpCodes.Ldc_I4_5); break;
                case 6: il.Emit(OpCodes.Ldc_I4_6); break;
                case 7: il.Emit(OpCodes.Ldc_I4_7); break;
                case 8: il.Emit(OpCodes.Ldc_I4_8); break;
                default:
                    if (value >= -128 && value <= 127)
                    {
                        il.Emit(OpCodes.Ldc_I4_S, (sbyte)value);
                    }
                    else
                    {
                        il.Emit(OpCodes.Ldc_I4, value);
                    }
                    break;
            }
        }


        /// <summary>
        /// Key used to indicate the type name associated with a DataTable
        /// </summary>
        private const string DataTableTypeNameKey = "dapper:TypeName";

        /// <summary>
        /// How should connection strings be compared for equivalence? Defaults to StringComparer.Ordinal.
        /// Providing a custom implementation can be useful for allowing multi-tenancy databases with identical
        /// schema to share strategies. Note that usual equivalence rules apply: any equivalent connection strings
        /// <b>MUST</b> yield the same hash-code.
        /// </summary>
        public static IEqualityComparer<string> ConnectionStringComparer
        {
            get { return connectionStringComparer; }
            set { connectionStringComparer = value ?? StringComparer.Ordinal; }
        }
        private static IEqualityComparer<string> connectionStringComparer = StringComparer.Ordinal;


        /// <summary>
        /// The grid reader provides interfaces for reading multiple result sets from a Dapper query 
        /// </summary>
        public partial class GridReader : IDisposable
        {
            private IDataReader reader;
            private IDbCommand command;
            private Identity identity;
            private bool addToCache;

            internal GridReader(IDbCommand command, IDataReader reader, Identity identity, SqlMapper.IParameterCallbacks callbacks, bool addToCache)
            {
                this.command = command;
                this.reader = reader;
                this.identity = identity;
                this.callbacks = callbacks;
                this.addToCache = addToCache;
            }

#if !CSHARP30

            /// <summary>
            /// Read the next grid of results, returned as a dynamic object
            /// </summary>
            /// <remarks>Note: each row can be accessed via "dynamic", or by casting to an IDictionary&lt;string,object&gt;</remarks>
            public IEnumerable<dynamic> Read(bool buffered = true)
            {
                return ReadImpl<dynamic>(typeof(DapperRow), buffered);
            }
#endif

#if CSHARP30
            /// <summary>
            /// Read the next grid of results
            /// </summary>
            public IEnumerable<T> Read<T>()
            {
                return Read<T>(true);
            }
#endif
            /// <summary>
            /// Read the next grid of results
            /// </summary>
#if CSHARP30
            public IEnumerable<T> Read<T>(bool buffered)
#else
            public IEnumerable<T> Read<T>(bool buffered = true)
#endif
            {
                return ReadImpl<T>(typeof(T), buffered);
            }

            /// <summary>
            /// Read the next grid of results
            /// </summary>
#if CSHARP30
            public IEnumerable<object> Read(Type type, bool buffered)
#else
            public IEnumerable<object> Read(Type type, bool buffered = true)
#endif
            {
                if (type == null) throw new ArgumentNullException("type");
                return ReadImpl<object>(type, buffered);
            }

            private IEnumerable<T> ReadImpl<T>(Type type, bool buffered)
            {
                if (reader == null) throw new ObjectDisposedException(GetType().FullName, "The reader has been disposed; this can happen after all data has been consumed");
                if (consumed) throw new InvalidOperationException("Query results must be consumed in the correct order, and each result can only be consumed once");
                var typedIdentity = identity.ForGrid(type, gridIndex);
                CacheInfo cache = GetCacheInfo(typedIdentity, null, addToCache);
                var deserializer = cache.Deserializer;

                int hash = GetColumnHash(reader);
                if (deserializer.Func == null || deserializer.Hash != hash)
                {
                    deserializer = new DeserializerState(hash, GetDeserializer(type, reader, 0, -1, false));
                    cache.Deserializer = deserializer;
                }
                consumed = true;
                var result = ReadDeferred<T>(gridIndex, deserializer.Func, typedIdentity);
                return buffered ? result.ToList() : result;
            }


            private IEnumerable<TReturn> MultiReadInternal<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TSeventh, TReturn>(Delegate func, string splitOn)
            {
                var identity = this.identity.ForGrid(typeof(TReturn), new Type[] { 
                    typeof(TFirst), 
                    typeof(TSecond),
                    typeof(TThird),
                    typeof(TFourth),
                    typeof(TFifth),
                    typeof(TSixth),
                    typeof(TSeventh)
                }, gridIndex);
                try
                {
                    foreach (var r in SqlMapper.MultiMapImpl<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TSeventh, TReturn>(null, default(CommandDefinition), func, splitOn, reader, identity, false))
                    {
                        yield return r;
                    }
                }
                finally
                {
                    NextResult();
                }
            }

#if CSHARP30
            /// <summary>
            /// Read multiple objects from a single record set on the grid
            /// </summary>
            public IEnumerable<TReturn> Read<TFirst, TSecond, TReturn>(Func<TFirst, TSecond, TReturn> func, string splitOn)
            {
                return Read<TFirst, TSecond, TReturn>(func, splitOn, true);
            }
#endif
            /// <summary>
            /// Read multiple objects from a single record set on the grid
            /// </summary>
#if CSHARP30
            public IEnumerable<TReturn> Read<TFirst, TSecond, TReturn>(Func<TFirst, TSecond, TReturn> func, string splitOn, bool buffered)
#else
            public IEnumerable<TReturn> Read<TFirst, TSecond, TReturn>(Func<TFirst, TSecond, TReturn> func, string splitOn = "id", bool buffered = true)
#endif
            {
                var result = MultiReadInternal<TFirst, TSecond, DontMap, DontMap, DontMap, DontMap, DontMap, TReturn>(func, splitOn);
                return buffered ? result.ToList() : result;
            }

#if CSHARP30
            /// <summary>
            /// Read multiple objects from a single record set on the grid
            /// </summary>
            public IEnumerable<TReturn> Read<TFirst, TSecond, TThird, TReturn>(Func<TFirst, TSecond, TThird, TReturn> func, string splitOn)
            {
                return Read<TFirst, TSecond, TThird, TReturn>(func, splitOn, true);
            }
#endif
            /// <summary>
            /// Read multiple objects from a single record set on the grid
            /// </summary>
#if CSHARP30
            public IEnumerable<TReturn> Read<TFirst, TSecond, TThird, TReturn>(Func<TFirst, TSecond, TThird, TReturn> func, string splitOn, bool buffered)
#else
            public IEnumerable<TReturn> Read<TFirst, TSecond, TThird, TReturn>(Func<TFirst, TSecond, TThird, TReturn> func, string splitOn = "id", bool buffered = true)
#endif
            {
                var result = MultiReadInternal<TFirst, TSecond, TThird, DontMap, DontMap, DontMap, DontMap, TReturn>(func, splitOn);
                return buffered ? result.ToList() : result;
            }

#if CSHARP30
            /// <summary>
            /// Read multiple objects from a single record set on the grid
            /// </summary>
            public IEnumerable<TReturn> Read<TFirst, TSecond, TThird, TFourth, TReturn>(Func<TFirst, TSecond, TThird, TFourth, TReturn> func, string splitOn)
            {
                return Read<TFirst, TSecond, TThird, TFourth, TReturn>(func, splitOn, true);
            }
#endif

            /// <summary>
            /// Read multiple objects from a single record set on the grid
            /// </summary>
#if CSHARP30
            public IEnumerable<TReturn> Read<TFirst, TSecond, TThird, TFourth, TReturn>(Func<TFirst, TSecond, TThird, TFourth, TReturn> func, string splitOn, bool buffered)
#else
            public IEnumerable<TReturn> Read<TFirst, TSecond, TThird, TFourth, TReturn>(Func<TFirst, TSecond, TThird, TFourth, TReturn> func, string splitOn = "id", bool buffered = true)
#endif
            {
                var result = MultiReadInternal<TFirst, TSecond, TThird, TFourth, DontMap, DontMap, DontMap, TReturn>(func, splitOn);
                return buffered ? result.ToList() : result;
            }



#if !CSHARP30
            /// <summary>
            /// Read multiple objects from a single record set on the grid
            /// </summary>
            public IEnumerable<TReturn> Read<TFirst, TSecond, TThird, TFourth, TFifth, TReturn>(Func<TFirst, TSecond, TThird, TFourth, TFifth, TReturn> func, string splitOn = "id", bool buffered = true)
            {
                var result = MultiReadInternal<TFirst, TSecond, TThird, TFourth, TFifth, DontMap, DontMap, TReturn>(func, splitOn);
                return buffered ? result.ToList() : result;
            }
            /// <summary>
            /// Read multiple objects from a single record set on the grid
            /// </summary>
            public IEnumerable<TReturn> Read<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TReturn>(Func<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TReturn> func, string splitOn = "id", bool buffered = true)
            {
                var result = MultiReadInternal<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, DontMap, TReturn>(func, splitOn);
                return buffered ? result.ToList() : result;
            }
            /// <summary>
            /// Read multiple objects from a single record set on the grid
            /// </summary>
            public IEnumerable<TReturn> Read<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TSeventh, TReturn>(Func<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TSeventh, TReturn> func, string splitOn = "id", bool buffered = true)
            {
                var result = MultiReadInternal<TFirst, TSecond, TThird, TFourth, TFifth, TSixth, TSeventh, TReturn>(func, splitOn);
                return buffered ? result.ToList() : result;
            }
#endif

            private IEnumerable<T> ReadDeferred<T>(int index, Func<IDataReader, object> deserializer, Identity typedIdentity)
            {
                try
                {
                    while (index == gridIndex && reader.Read())
                    {
                        yield return (T)deserializer(reader);
                    }
                }
                finally // finally so that First etc progresses things even when multiple rows
                {
                    if (index == gridIndex)
                    {
                        NextResult();
                    }
                }
            }
            private int gridIndex, readCount;
            private bool consumed;
            private SqlMapper.IParameterCallbacks callbacks;

            /// <summary>
            /// Has the underlying reader been consumed?
            /// </summary>
            public bool IsConsumed
            {
                get
                {
                    return consumed;
                }
            }
            private void NextResult()
            {
                if (reader.NextResult())
                {
                    readCount++;
                    gridIndex++;
                    consumed = false;
                }
                else
                {
                    // happy path; close the reader cleanly - no
                    // need for "Cancel" etc
                    reader.Dispose();
                    reader = null;
                    if (callbacks != null) callbacks.OnCompleted();
                    Dispose();
                }
            }
            /// <summary>
            /// Dispose the grid, closing and disposing both the underlying reader and command.
            /// </summary>
            public void Dispose()
            {
                if (reader != null)
                {
                    if (!reader.IsClosed && command != null) command.Cancel();
                    reader.Dispose();
                    reader = null;
                }
                if (command != null)
                {
                    command.Dispose();
                    command = null;
                }
            }
        }


#if !DNXCORE50
        /// <summary>
        /// Used to pass a DataTable as a TableValuedParameter
        /// </summary>
        public static ICustomQueryParameter AsTableValuedParameter(this DataTable table, string typeName
#if !CSHARP30
            = null
#endif
            )
        {
            return new TableValuedParameter(table, typeName);
        }

        /// <summary>
        /// Associate a DataTable with a type name
        /// </summary>
        public static void SetTypeName(this DataTable table, string typeName)
        {
            if (table != null)
            {
                if (string.IsNullOrEmpty(typeName))
                    table.ExtendedProperties.Remove(DataTableTypeNameKey);
                else
                    table.ExtendedProperties[DataTableTypeNameKey] = typeName;
            }
        }

        /// <summary>
        /// Fetch the type name associated with a DataTable
        /// </summary>
        public static string GetTypeName(this DataTable table)
        {
            return table == null ? null : table.ExtendedProperties[DataTableTypeNameKey] as string;
        }
#endif

        // one per thread
        [ThreadStatic]
        private static StringBuilder perThreadStringBuilderCache;
        private static StringBuilder GetStringBuilder()
        {
            var tmp = perThreadStringBuilderCache;
            if (tmp != null)
            {
                perThreadStringBuilderCache = null;
                tmp.Length = 0;
                return tmp;
            }
            return new StringBuilder();
        }

        private static string __ToStringRecycle(this StringBuilder obj)
        {
            if (obj == null) return "";
            var s = obj.ToString();
            if(perThreadStringBuilderCache == null)
            {
                perThreadStringBuilderCache = obj;
            }
            return s;
        }
    }

    /// <summary>
    /// A bag of parameters that can be passed to the Dapper Query and Execute methods
    /// </summary>
    partial class DynamicParameters : SqlMapper.IDynamicParameters, SqlMapper.IParameterLookup, SqlMapper.IParameterCallbacks
    {
        internal const DbType EnumerableMultiParameter = (DbType)(-1);
        static Dictionary<SqlMapper.Identity, Action<IDbCommand, object>> paramReaderCache = new Dictionary<SqlMapper.Identity, Action<IDbCommand, object>>();

        Dictionary<string, ParamInfo> parameters = new Dictionary<string, ParamInfo>();
        List<object> templates;

        object SqlMapper.IParameterLookup.this[string member]
        {
            get
            {
                ParamInfo param;
                return parameters.TryGetValue(member, out param) ? param.Value : null;
            }
        }

        partial class ParamInfo
        {
            public string Name { get; set; }
            public object Value { get; set; }
            public ParameterDirection ParameterDirection { get; set; }
            public DbType? DbType { get; set; }
            public int? Size { get; set; }
            public IDbDataParameter AttachedParam { get; set; }
            internal Action<object, DynamicParameters> OutputCallback { get; set; }
            internal object OutputTarget { get; set; }
            internal bool CameFromTemplate { get; set; }

            public byte? Precision { get; set; }
            public byte? Scale { get; set; }
        }

        /// <summary>
        /// construct a dynamic parameter bag
        /// </summary>
        public DynamicParameters()
        {
            RemoveUnused = true;
        }

        /// <summary>
        /// construct a dynamic parameter bag
        /// </summary>
        /// <param name="template">can be an anonymous type or a DynamicParameters bag</param>
        public DynamicParameters(object template)
        {
            RemoveUnused = true;
            AddDynamicParams(template);
        }

        /// <summary>
        /// Append a whole object full of params to the dynamic
        /// EG: AddDynamicParams(new {A = 1, B = 2}) // will add property A and B to the dynamic
        /// </summary>
        /// <param name="param"></param>
        public void AddDynamicParams(object param)
        {
            var obj = param as object;
            if (obj != null)
            {
                var subDynamic = obj as DynamicParameters;
                if (subDynamic == null)
                {
                    var dictionary = obj as IEnumerable<KeyValuePair<string, object>>;
                    if (dictionary == null)
                    {
                        templates = templates ?? new List<object>();
                        templates.Add(obj);
                    }
                    else
                    {
                        foreach (var kvp in dictionary)
                        {
                            Add(kvp.Key, kvp.Value, null, null, null);
                        }
                    }
                }
                else
                {
                    if (subDynamic.parameters != null)
                    {
                        foreach (var kvp in subDynamic.parameters)
                        {
                            parameters.Add(kvp.Key, kvp.Value);
                        }
                    }

                    if (subDynamic.templates != null)
                    {
                        templates = templates ?? new List<object>();
                        foreach (var t in subDynamic.templates)
                        {
                            templates.Add(t);
                        }
                    }
                }
            }
        }

        /// <summary>
        /// Add a parameter to this dynamic parameter list
        /// </summary>
        public void Add(string name, object value, DbType? dbType, ParameterDirection? direction, int? size)
        {
            parameters[Clean(name)] = new ParamInfo() {
                Name = name, Value = value, ParameterDirection = direction ?? ParameterDirection.Input,
                DbType = dbType, Size = size
            };
        }

        /// <summary>
        /// Add a parameter to this dynamic parameter list
        /// </summary>
        public void Add(
#if CSHARP30
string name, object value, DbType? dbType, ParameterDirection? direction, int? size, byte? precision, byte? scale
#else
string name, object value = null, DbType? dbType = null, ParameterDirection? direction = null, int? size = null, byte? precision = null, byte? scale = null
#endif
)
        {
            parameters[Clean(name)] = new ParamInfo() {
                Name = name, Value = value, ParameterDirection = direction ?? ParameterDirection.Input,
                DbType = dbType, Size = size,
                Precision = precision, Scale = scale
            };
        }

        static string Clean(string name)
        {
            if (!string.IsNullOrEmpty(name))
            {
                switch (name[0])
                {
                    case '@':
                    case ':':
                    case '?':
                        return name.Substring(1);
                }
            }
            return name;
        }

        void SqlMapper.IDynamicParameters.AddParameters(IDbCommand command, SqlMapper.Identity identity)
        {
            AddParameters(command, identity);
        }

        /// <summary>
        /// If true, the command-text is inspected and only values that are clearly used are included on the connection
        /// </summary>
        public bool RemoveUnused { get; set; }

        /// <summary>
        /// Add all the parameters needed to the command just before it executes
        /// </summary>
        /// <param name="command">The raw command prior to execution</param>
        /// <param name="identity">Information about the query</param>
        protected void AddParameters(IDbCommand command, SqlMapper.Identity identity)
        {
            var literals = SqlMapper.GetLiteralTokens(identity.sql);

            if (templates != null)
            {
                foreach (var template in templates)
                {
                    var newIdent = identity.ForDynamicParameters(template.GetType());
                    Action<IDbCommand, object> appender;

                    lock (paramReaderCache)
                    {
                        if (!paramReaderCache.TryGetValue(newIdent, out appender))
                        {
                            appender = SqlMapper.CreateParamInfoGenerator(newIdent, true, RemoveUnused, literals);
                            paramReaderCache[newIdent] = appender;
                        }
                    }

                    appender(command, template);
                }

                // The parameters were added to the command, but not the 
                // DynamicParameters until now.
                foreach (IDbDataParameter param in command.Parameters)
                {
                    // If someone makes a DynamicParameters with a template,
                    // then explicitly adds a parameter of a matching name,
                    // it will already exist in 'parameters'.
                    if (!parameters.ContainsKey(param.ParameterName)) 
                    {
                        parameters.Add(param.ParameterName, new ParamInfo
                        {
                            AttachedParam = param,
                            CameFromTemplate = true,
                            DbType = param.DbType,
                            Name = param.ParameterName,
                            ParameterDirection = param.Direction,
                            Size = param.Size,
                            Value = param.Value
                        });
                    }
                }

                // Now that the parameters are added to the command, let's place our output callbacks
                var tmp = outputCallbacks;
                if (tmp != null)
                {
                    foreach (var generator in tmp)
                    {
                        generator();
                    }
                }
            }

            foreach (var param in parameters.Values)
            {
                if (param.CameFromTemplate) continue;

                var dbType = param.DbType;
                var val = param.Value;
                string name = Clean(param.Name);
                var isCustomQueryParameter = val is SqlMapper.ICustomQueryParameter;

                SqlMapper.ITypeHandler handler = null;
                if (dbType == null && val != null && !isCustomQueryParameter) dbType = SqlMapper.LookupDbType(val.GetType(), name, true, out handler);
                if (dbType == DynamicParameters.EnumerableMultiParameter)
                {
#pragma warning disable 612, 618
                    SqlMapper.PackListParameters(command, name, val);
#pragma warning restore 612, 618
                }
                else if (isCustomQueryParameter)
                {
                    ((SqlMapper.ICustomQueryParameter)val).AddParameter(command, name);
                }
                else
                {

                    bool add = !command.Parameters.Contains(name);
                    IDbDataParameter p;
                    if (add)
                    {
                        p = command.CreateParameter();
                        p.ParameterName = name;
                    }
                    else
                    {
                        p = (IDbDataParameter)command.Parameters[name];
                    }

                    p.Direction = param.ParameterDirection;
                    if (handler == null)
                    {
                        p.Value = SqlMapper.SanitizeParameterValue(val);
                        if (dbType != null && p.DbType != dbType)
                        {
                            p.DbType = dbType.Value;
                        }
                        var s = val as string;
                        if (s != null)
                        {
                            if (s.Length <= DbString.DefaultLength)
                            {
                                p.Size = DbString.DefaultLength;
                            }
                        }
                        if (param.Size != null) p.Size = param.Size.Value;
                        if (param.Precision != null) p.Precision = param.Precision.Value;
                        if (param.Scale != null) p.Scale = param.Scale.Value;
                    }
                    else
                    {
                        if (dbType != null) p.DbType = dbType.Value;
                        if (param.Size != null) p.Size = param.Size.Value;
                        if (param.Precision != null) p.Precision = param.Precision.Value;
                        if (param.Scale != null) p.Scale = param.Scale.Value;
                        handler.SetValue(p, val ?? DBNull.Value);
                    }

                    if (add)
                    {
                        command.Parameters.Add(p);
                    }
                    param.AttachedParam = p;
                }
            }

            // note: most non-priveleged implementations would use: this.ReplaceLiterals(command);
            if(literals.Count != 0) SqlMapper.ReplaceLiterals(this, command, literals);
        }

        /// <summary>
        /// All the names of the param in the bag, use Get to yank them out
        /// </summary>
        public IEnumerable<string> ParameterNames
        {
            get
            {
                return parameters.Select(p => p.Key);
            }
        }


        /// <summary>
        /// Get the value of a parameter
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="name"></param>
        /// <returns>The value, note DBNull.Value is not returned, instead the value is returned as null</returns>
        public T Get<T>(string name)
        {
            var paramInfo = parameters[Clean(name)];
            var attachedParam = paramInfo.AttachedParam;
            object val = attachedParam == null ? paramInfo.Value : attachedParam.Value;
            if (val == DBNull.Value)
            {
                if (default(T) != null)
                {
                    throw new ApplicationException("Attempting to cast a DBNull to a non nullable type! Note that out/return parameters will not have updated values until the data stream completes (after the 'foreach' for Query(..., buffered: false), or after the GridReader has been disposed for QueryMultiple)");
                }
                return default(T);
            }
            return (T)val;
        }

        /// <summary>
        /// Allows you to automatically populate a target property/field from output parameters. It actually
        /// creates an InputOutput parameter, so you can still pass data in. 
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="target">The object whose property/field you wish to populate.</param>
        /// <param name="expression">A MemberExpression targeting a property/field of the target (or descendant thereof.)</param>
        /// <param name="dbType"></param>
        /// <param name="size">The size to set on the parameter. Defaults to 0, or DbString.DefaultLength in case of strings.</param>
        /// <returns>The DynamicParameters instance</returns>
#if CSHARP30
        public DynamicParameters Output<T>(T target, Expression<Func<T, object>> expression, DbType? dbType, int? size)
#else
        public DynamicParameters Output<T>(T target, Expression<Func<T, object>> expression, DbType? dbType = null, int? size = null)
#endif
        {
            var failMessage = "Expression must be a property/field chain off of a(n) {0} instance";
            failMessage = string.Format(failMessage, typeof(T).Name);
            Action @throw = () => { throw new InvalidOperationException(failMessage); };

            // Is it even a MemberExpression?
            var lastMemberAccess = expression.Body as MemberExpression;

            if (lastMemberAccess == null ||
                (!(lastMemberAccess.Member is PropertyInfo) &&
                !(lastMemberAccess.Member is FieldInfo)))
            {
                if (expression.Body.NodeType == ExpressionType.Convert &&
                    expression.Body.Type == typeof(object) &&
                    ((UnaryExpression)expression.Body).Operand is MemberExpression)
                {
                    // It's got to be unboxed
                    lastMemberAccess = (MemberExpression)((UnaryExpression)expression.Body).Operand;
                }
                else @throw();
            }

            // Does the chain consist of MemberExpressions leading to a ParameterExpression of type T?
            MemberExpression diving = lastMemberAccess;
            ParameterExpression constant = null;
            // Retain a list of member names and the member expressions so we can rebuild the chain.
            List<string> names = new List<string>();
            List<MemberExpression> chain = new List<MemberExpression>();

            do
            {
                // Insert the names in the right order so expression 
                // "Post.Author.Name" becomes parameter "PostAuthorName"
                names.Insert(0, diving.Member.Name);
                chain.Insert(0, diving);

                constant = diving.Expression as ParameterExpression;
                diving = diving.Expression as MemberExpression;

                if (constant != null &&
                    constant.Type == typeof(T))
                {
                    break;
                }
                else if (diving == null ||
                    (!(diving.Member is PropertyInfo) &&
                    !(diving.Member is FieldInfo)))
                {
                    @throw();
                }
            }
            while (diving != null);

            var dynamicParamName = string.Join(string.Empty, names.ToArray());

            // Before we get all emitty...
            var lookup = string.Join("|", names.ToArray());

            var cache = CachedOutputSetters<T>.Cache;
            Action<object, DynamicParameters> setter;
#if DNXCORE50
            lock (cache)
            {
                if(!cache.TryGetValue(lookup, out setter)) setter = null;
            }
#else
            setter = (Action<object, DynamicParameters>)cache[lookup];
#endif
            if (setter != null) goto MAKECALLBACK;

            // Come on let's build a method, let's build it, let's build it now!
            var dm = new DynamicMethod(string.Format("ExpressionParam{0}", Guid.NewGuid()), null, new[] { typeof(object), this.GetType() }, true);
            var il = dm.GetILGenerator();

            il.Emit(OpCodes.Ldarg_0); // [object]
            il.Emit(OpCodes.Castclass, typeof(T));    // [T]

            // Count - 1 to skip the last member access
            var i = 0;
            for (; i < (chain.Count - 1); i++)
            {
                var member = chain[0].Member;

                if (member is PropertyInfo)
                {
                    var get = ((PropertyInfo)member).GetGetMethod(true);
                    il.Emit(OpCodes.Callvirt, get); // [Member{i}]
                }
                else // Else it must be a field!
                {
                    il.Emit(OpCodes.Ldfld, ((FieldInfo)member)); // [Member{i}]
                }
            }

            var paramGetter = this.GetType().GetMethod("Get", new Type[] { typeof(string) }).MakeGenericMethod(lastMemberAccess.Type);

            il.Emit(OpCodes.Ldarg_1); // [target] [DynamicParameters]
            il.Emit(OpCodes.Ldstr, dynamicParamName); // [target] [DynamicParameters] [ParamName]
            il.Emit(OpCodes.Callvirt, paramGetter); // [target] [value], it's already typed thanks to generic method
            
            // GET READY
            var lastMember = lastMemberAccess.Member;
            if (lastMember is PropertyInfo)
            {
                var set = ((PropertyInfo)lastMember).GetSetMethod(true);
                il.Emit(OpCodes.Callvirt, set); // SET
            }
            else
            {
                il.Emit(OpCodes.Stfld, ((FieldInfo)lastMember)); // SET
            }

            il.Emit(OpCodes.Ret); // GO

            setter = (Action<object, DynamicParameters>)dm.CreateDelegate(typeof(Action<object, DynamicParameters>));
            lock (cache)
            {
                cache[lookup] = setter;
            }

            // Queue the preparation to be fired off when adding parameters to the DbCommand
            MAKECALLBACK:
            (outputCallbacks ?? (outputCallbacks = new List<Action>())).Add(() =>
            {
                // Finally, prep the parameter and attach the callback to it
                ParamInfo parameter;
                var targetMemberType = lastMemberAccess.Type;
                int sizeToSet = (!size.HasValue && targetMemberType == typeof(string)) ? DbString.DefaultLength : size ?? 0;

                if (this.parameters.TryGetValue(dynamicParamName, out parameter))
                {
                    parameter.ParameterDirection = parameter.AttachedParam.Direction = ParameterDirection.InputOutput;

                    if (parameter.AttachedParam.Size == 0)
                    {
                        parameter.Size = parameter.AttachedParam.Size = sizeToSet;
                    }
                }
                else
                {
                    SqlMapper.ITypeHandler handler;
                    dbType = (!dbType.HasValue) ? SqlMapper.LookupDbType(targetMemberType, targetMemberType.Name, true, out handler) : dbType;

                    // CameFromTemplate property would not apply here because this new param
                    // Still needs to be added to the command
                    this.Add(dynamicParamName, expression.Compile().Invoke(target), null, ParameterDirection.InputOutput, sizeToSet);
                }

                parameter = this.parameters[dynamicParamName];
                parameter.OutputCallback = setter;
                parameter.OutputTarget = target;
            });

            return this;
        }

        private List<Action> outputCallbacks;

        private readonly Dictionary<string, Action<object, DynamicParameters>> cachedOutputSetters = new Dictionary<string,Action<object,DynamicParameters>>();

        internal static class CachedOutputSetters<T>
        {
#if DNXCORE50
            public static readonly Dictionary<string, Action<object, DynamicParameters>> Cache = new Dictionary<string, Action<object, DynamicParameters>>();
#else
            public static readonly Hashtable Cache = new Hashtable();
#endif
        }

        void SqlMapper.IParameterCallbacks.OnCompleted()
        {
            foreach (var param in (from p in parameters select p.Value))
            {
                if (param.OutputCallback != null) param.OutputCallback(param.OutputTarget, this);
            }
        }
    }
#if !DNXCORE50
    sealed class DataTableHandler : Dapper.SqlMapper.ITypeHandler
    {
        public object Parse(Type destinationType, object value)
        {
            throw new NotImplementedException();
        }

        public void SetValue(IDbDataParameter parameter, object value)
        {
            TableValuedParameter.Set(parameter, value as DataTable, null);
        }
    }

    /// <summary>
    /// Used to pass a DataTable as a TableValuedParameter
    /// </summary>
    sealed partial class TableValuedParameter : Dapper.SqlMapper.ICustomQueryParameter
    {
        private readonly DataTable table;
        private readonly string typeName;

        /// <summary>
        /// Create a new instance of TableValuedParameter
        /// </summary>
        public TableValuedParameter(DataTable table) : this(table, null) { }
        /// <summary>
        /// Create a new instance of TableValuedParameter
        /// </summary>
        public TableValuedParameter(DataTable table, string typeName)
        {
            this.table = table;
            this.typeName = typeName;
        }
        static readonly Action<System.Data.SqlClient.SqlParameter, string> setTypeName;
        static TableValuedParameter()
        {
            var prop = typeof(System.Data.SqlClient.SqlParameter).GetProperty("TypeName", BindingFlags.Instance | BindingFlags.Public);
            if(prop != null && prop.PropertyType == typeof(string) && prop.CanWrite)
            {
                setTypeName = (Action<System.Data.SqlClient.SqlParameter, string>)
                    Delegate.CreateDelegate(typeof(Action<System.Data.SqlClient.SqlParameter, string>), prop.GetSetMethod());
            }
        }
        void SqlMapper.ICustomQueryParameter.AddParameter(IDbCommand command, string name)
        {
            var param = command.CreateParameter();
            param.ParameterName = name;
            Set(param, table, typeName);
            command.Parameters.Add(param);
        }
        internal static void Set(IDbDataParameter parameter, DataTable table, string typeName)
        {
            parameter.Value = SqlMapper.SanitizeParameterValue(table);
            if (string.IsNullOrEmpty(typeName) && table != null)
            {
                typeName = SqlMapper.GetTypeName(table);
            }
            if (!string.IsNullOrEmpty(typeName))
            {
                var sqlParam = parameter as System.Data.SqlClient.SqlParameter;
                if (sqlParam != null)
                {
                    if (setTypeName != null) setTypeName(sqlParam, typeName);
                    sqlParam.SqlDbType = SqlDbType.Structured;
                }
            }
        }
    }
#endif
    /// <summary>
    /// This class represents a SQL string, it can be used if you need to denote your parameter is a Char vs VarChar vs nVarChar vs nChar
    /// </summary>
    sealed partial class DbString : Dapper.SqlMapper.ICustomQueryParameter
    {
        /// <summary>
        /// A value to set the default value of strings
        /// going through Dapper. Default is 4000, any value larger than this
        /// field will not have the default value applied.
        /// </summary>
        public const int DefaultLength = 4000;

        /// <summary>
        /// Create a new DbString
        /// </summary>
        public DbString() { Length = -1; }
        /// <summary>
        /// Ansi vs Unicode 
        /// </summary>
        public bool IsAnsi { get; set; }
        /// <summary>
        /// Fixed length 
        /// </summary>
        public bool IsFixedLength { get; set; }
        /// <summary>
        /// Length of the string -1 for max
        /// </summary>
        public int Length { get; set; }
        /// <summary>
        /// The value of the string
        /// </summary>
        public string Value { get; set; }
        /// <summary>
        /// Add the parameter to the command... internal use only
        /// </summary>
        /// <param name="command"></param>
        /// <param name="name"></param>
        public void AddParameter(IDbCommand command, string name)
        {
            if (IsFixedLength && Length == -1)
            {
                throw new InvalidOperationException("If specifying IsFixedLength,  a Length must also be specified");
            }
            var param = command.CreateParameter();
            param.ParameterName = name;
            param.Value = SqlMapper.SanitizeParameterValue(Value);
            if (Length == -1 && Value != null && Value.Length <= DefaultLength)
            {
                param.Size = DefaultLength;
            }
            else
            {
                param.Size = Length;
            }
            param.DbType = IsAnsi ? (IsFixedLength ? DbType.AnsiStringFixedLength : DbType.AnsiString) : (IsFixedLength ? DbType.StringFixedLength : DbType.String);
            command.Parameters.Add(param);
        }
    }

    /// <summary>
    /// Handles variances in features per DBMS
    /// </summary>
    partial class FeatureSupport
    {
        private static readonly FeatureSupport
            @default = new FeatureSupport(false),
            postgres = new FeatureSupport(true);

        /// <summary>
        /// Gets the feature set based on the passed connection
        /// </summary>
        public static FeatureSupport Get(IDbConnection connection)
        {
            string name = connection == null ? null : connection.GetType().Name;
            if (string.Equals(name, "npgsqlconnection", StringComparison.OrdinalIgnoreCase)) return postgres;
            return @default;
        }
        private FeatureSupport(bool arrays)
        {
            Arrays = arrays;
        }
        /// <summary>
        /// True if the db supports array columns e.g. Postgresql
        /// </summary>
        public bool Arrays { get; private set; }
    }

    /// <summary>
    /// Represents simple member map for one of target parameter or property or field to source DataReader column
    /// </summary>
    sealed partial class SimpleMemberMap : SqlMapper.IMemberMap
    {
        private readonly string _columnName;
        private readonly PropertyInfo _property;
        private readonly FieldInfo _field;
        private readonly ParameterInfo _parameter;

        /// <summary>
        /// Creates instance for simple property mapping
        /// </summary>
        /// <param name="columnName">DataReader column name</param>
        /// <param name="property">Target property</param>
        public SimpleMemberMap(string columnName, PropertyInfo property)
        {
            if (columnName == null)
                throw new ArgumentNullException("columnName");

            if (property == null)
                throw new ArgumentNullException("property");

            _columnName = columnName;
            _property = property;
        }

        /// <summary>
        /// Creates instance for simple field mapping
        /// </summary>
        /// <param name="columnName">DataReader column name</param>
        /// <param name="field">Target property</param>
        public SimpleMemberMap(string columnName, FieldInfo field)
        {
            if (columnName == null)
                throw new ArgumentNullException("columnName");

            if (field == null)
                throw new ArgumentNullException("field");

            _columnName = columnName;
            _field = field;
        }

        /// <summary>
        /// Creates instance for simple constructor parameter mapping
        /// </summary>
        /// <param name="columnName">DataReader column name</param>
        /// <param name="parameter">Target constructor parameter</param>
        public SimpleMemberMap(string columnName, ParameterInfo parameter)
        {
            if (columnName == null)
                throw new ArgumentNullException("columnName");

            if (parameter == null)
                throw new ArgumentNullException("parameter");

            _columnName = columnName;
            _parameter = parameter;
        }

        /// <summary>
        /// DataReader column name
        /// </summary>
        public string ColumnName
        {
            get { return _columnName; }
        }

        /// <summary>
        /// Target member type
        /// </summary>
        public Type MemberType
        {
            get
            {
                if (_field != null)
                    return _field.FieldType;

                if (_property != null)
                    return _property.PropertyType;

                if (_parameter != null)
                    return _parameter.ParameterType;

                return null;
            }
        }

        /// <summary>
        /// Target property
        /// </summary>
        public PropertyInfo Property
        {
            get { return _property; }
        }

        /// <summary>
        /// Target field
        /// </summary>
        public FieldInfo Field
        {
            get { return _field; }
        }

        /// <summary>
        /// Target constructor parameter
        /// </summary>
        public ParameterInfo Parameter
        {
            get { return _parameter; }
        }
    }

    /// <summary>
    /// Represents default type mapping strategy used by Dapper
    /// </summary>
    sealed partial class DefaultTypeMap : SqlMapper.ITypeMap
    {
        private readonly List<FieldInfo> _fields;
        private readonly List<PropertyInfo> _properties;
        private readonly Type _type;

        /// <summary>
        /// Creates default type map
        /// </summary>
        /// <param name="type">Entity type</param>
        public DefaultTypeMap(Type type)
        {
            if (type == null)
                throw new ArgumentNullException("type");

            _fields = GetSettableFields(type);
            _properties = GetSettableProps(type);
            _type = type;
        }
#if DNXCORE50
        static bool IsParameterMatch(ParameterInfo[] x, ParameterInfo[] y)
        {
            if (ReferenceEquals(x, y)) return true;
            if (x == null || y == null) return false;
            if (x.Length != y.Length) return false;
            for (int i = 0; i < x.Length; i++)
                if (x[i].ParameterType != y[i].ParameterType) return false;
            return true;
        }
#endif
        internal static MethodInfo GetPropertySetter(PropertyInfo propertyInfo, Type type)
        {
            if (propertyInfo.DeclaringType == type) return propertyInfo.GetSetMethod(true);
#if DNXCORE50
            return propertyInfo.DeclaringType.GetProperties(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance)
                    .Single(x => x.Name == propertyInfo.Name
                        && x.PropertyType == propertyInfo.PropertyType
                        && IsParameterMatch(x.GetIndexParameters(), propertyInfo.GetIndexParameters())
                        ).GetSetMethod(true);
#else
            return propertyInfo.DeclaringType.GetProperty(
                   propertyInfo.Name,
                   BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance,
                   Type.DefaultBinder,
                   propertyInfo.PropertyType,
                   propertyInfo.GetIndexParameters().Select(p => p.ParameterType).ToArray(),
                   null).GetSetMethod(true);
#endif
        }

        internal static List<PropertyInfo> GetSettableProps(Type t)
        {
            return t
                  .GetProperties(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance)
                  .Where(p => GetPropertySetter(p, t) != null)
                  .ToList();
        }

        internal static List<FieldInfo> GetSettableFields(Type t)
        {
            return t.GetFields(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance).ToList();
        }

        /// <summary>
        /// Finds best constructor
        /// </summary>
        /// <param name="names">DataReader column names</param>
        /// <param name="types">DataReader column types</param>
        /// <returns>Matching constructor or default one</returns>
        public ConstructorInfo FindConstructor(string[] names, Type[] types)
        {
            var constructors = _type.GetConstructors(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
            foreach (ConstructorInfo ctor in constructors.OrderBy(c => c.IsPublic ? 0 : (c.IsPrivate ? 2 : 1)).ThenBy(c => c.GetParameters().Length))
            {
                ParameterInfo[] ctorParameters = ctor.GetParameters();
                if (ctorParameters.Length == 0)
                    return ctor;

                if (ctorParameters.Length != types.Length)
                    continue;

                int i = 0;
                for (; i < ctorParameters.Length; i++)
                {
                    if (!String.Equals(ctorParameters[i].Name, names[i], StringComparison.OrdinalIgnoreCase))
                        break;
                    if (types[i] == typeof(byte[]) && ctorParameters[i].ParameterType.FullName == SqlMapper.LinqBinary)
                        continue;
                    var unboxedType = Nullable.GetUnderlyingType(ctorParameters[i].ParameterType) ?? ctorParameters[i].ParameterType;
                    if (unboxedType != types[i]
                        && !(unboxedType.IsEnum() && Enum.GetUnderlyingType(unboxedType) == types[i])
                        && !(unboxedType == typeof(char) && types[i] == typeof(string))
                        && !(unboxedType.IsEnum() && types[i] == typeof(string)))
                    {
                        break;
                    }
                }

                if (i == ctorParameters.Length)
                    return ctor;
            }

            return null;
        }

        /// <summary>
        /// Returns the constructor, if any, that has the ExplicitConstructorAttribute on it.
        /// </summary>
        public ConstructorInfo FindExplicitConstructor()
        {
            var constructors = _type.GetConstructors(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);
#if DNXCORE50
            var withAttr = constructors.Where(c => c.CustomAttributes.Any(x => x.AttributeType == typeof(ExplicitConstructorAttribute))).ToList();
#else
            var withAttr = constructors.Where(c => c.GetCustomAttributes(typeof(ExplicitConstructorAttribute), true).Length > 0).ToList();
#endif

            if (withAttr.Count == 1)
            {
                return withAttr[0];
            }

            return null;
        }

        /// <summary>
        /// Gets mapping for constructor parameter
        /// </summary>
        /// <param name="constructor">Constructor to resolve</param>
        /// <param name="columnName">DataReader column name</param>
        /// <returns>Mapping implementation</returns>
        public SqlMapper.IMemberMap GetConstructorParameter(ConstructorInfo constructor, string columnName)
        {
            var parameters = constructor.GetParameters();

            return new SimpleMemberMap(columnName, parameters.FirstOrDefault(p => string.Equals(p.Name, columnName, StringComparison.OrdinalIgnoreCase)));
        }

        /// <summary>
        /// Gets member mapping for column
        /// </summary>
        /// <param name="columnName">DataReader column name</param>
        /// <returns>Mapping implementation</returns>
        public SqlMapper.IMemberMap GetMember(string columnName)
        {
            var property = _properties.FirstOrDefault(p => string.Equals(p.Name, columnName, StringComparison.Ordinal))
               ?? _properties.FirstOrDefault(p => string.Equals(p.Name, columnName, StringComparison.OrdinalIgnoreCase));

            if (property == null && MatchNamesWithUnderscores)
            {
                property = _properties.FirstOrDefault(p => string.Equals(p.Name, columnName.Replace("_", ""), StringComparison.Ordinal))
                    ?? _properties.FirstOrDefault(p => string.Equals(p.Name, columnName.Replace("_", ""), StringComparison.OrdinalIgnoreCase));
            }

            if (property != null)
                return new SimpleMemberMap(columnName, property);

            var field = _fields.FirstOrDefault(p => string.Equals(p.Name, columnName, StringComparison.Ordinal))
               ?? _fields.FirstOrDefault(p => string.Equals(p.Name, columnName, StringComparison.OrdinalIgnoreCase));

            if (field == null && MatchNamesWithUnderscores)
            {
                field = _fields.FirstOrDefault(p => string.Equals(p.Name, columnName.Replace("_", ""), StringComparison.Ordinal))
                    ?? _fields.FirstOrDefault(p => string.Equals(p.Name, columnName.Replace("_", ""), StringComparison.OrdinalIgnoreCase));
            }

            if (field != null)
                return new SimpleMemberMap(columnName, field);

            return null;
        }
        /// <summary>
        /// Should column names like User_Id be allowed to match properties/fields like UserId ?
        /// </summary>
        public static bool MatchNamesWithUnderscores { get; set; }
    }

    

    /// <summary>
    /// Implements custom property mapping by user provided criteria (usually presence of some custom attribute with column to member mapping)
    /// </summary>
    sealed partial class CustomPropertyTypeMap : SqlMapper.ITypeMap
    {
        private readonly Type _type;
        private readonly Func<Type, string, PropertyInfo> _propertySelector;

        /// <summary>
        /// Creates custom property mapping
        /// </summary>
        /// <param name="type">Target entity type</param>
        /// <param name="propertySelector">Property selector based on target type and DataReader column name</param>
        public CustomPropertyTypeMap(Type type, Func<Type, string, PropertyInfo> propertySelector)
        {
            if (type == null)
                throw new ArgumentNullException("type");

            if (propertySelector == null)
                throw new ArgumentNullException("propertySelector");

            _type = type;
            _propertySelector = propertySelector;
        }

        /// <summary>
        /// Always returns default constructor
        /// </summary>
        /// <param name="names">DataReader column names</param>
        /// <param name="types">DataReader column types</param>
        /// <returns>Default constructor</returns>
        public ConstructorInfo FindConstructor(string[] names, Type[] types)
        {
            return _type.GetConstructor(new Type[0]);
        }

        /// <summary>
        /// Always returns null
        /// </summary>
        /// <returns></returns>
        public ConstructorInfo FindExplicitConstructor()
        {
            return null;
        }

        /// <summary>
        /// Not implemented as far as default constructor used for all cases
        /// </summary>
        /// <param name="constructor"></param>
        /// <param name="columnName"></param>
        /// <returns></returns>
        public SqlMapper.IMemberMap GetConstructorParameter(ConstructorInfo constructor, string columnName)
        {
            throw new NotSupportedException();
        }

        /// <summary>
        /// Returns property based on selector strategy
        /// </summary>
        /// <param name="columnName">DataReader column name</param>
        /// <returns>Poperty member map</returns>
        public SqlMapper.IMemberMap GetMember(string columnName)
        {
            var prop = _propertySelector(_type, columnName);
            return prop != null ? new SimpleMemberMap(columnName, prop) : null;
        }
    }

#if DNXCORE50
    internal class WrappedReader : WrappedDataReader
    {
        private IDbCommand cmd;
        private IDataReader reader;

        public override IEnumerator GetEnumerator()
        {
            return Reader.GetEnumerator();
        }
        public WrappedReader(IDbCommand cmd, IDataReader reader)
        {
            this.cmd = cmd;
            this.reader = reader;
        }
        public override IDataReader Reader
        {
            get
            {
                var tmp = reader;
                if (tmp == null) throw new ObjectDisposedException(GetType().Name);
                return tmp;
            }
        }
        public override IDbCommand Command
        {
            get
            {
                var tmp = cmd;
                if (tmp == null) throw new ObjectDisposedException(GetType().Name);
                return tmp;
            }
        }

        public override int Depth
        {
            get { return Reader.Depth; }
        }

        public override bool IsClosed
        {
            get { return reader == null ? true : reader.IsClosed; }
        }
        public override bool HasRows
        {
            get
            {
                return Reader.HasRows;
            }
        }
        public override bool NextResult()
        {
            return Reader.NextResult();
        }

        public override bool Read()
        {
            return Reader.Read();
        }

        public override int RecordsAffected
        {
            get { return Reader.RecordsAffected; }
        }


        protected override void Dispose(bool disposing)
        {
            if (disposing)
            {
                if (reader != null) reader.Dispose();
                reader = null;
                if (cmd != null) cmd.Dispose();
                cmd = null;
            }
            base.Dispose(disposing);
        }

        public override int FieldCount
        {
            get { return Reader.FieldCount; }
        }

        public override bool GetBoolean(int i)
        {
            return Reader.GetBoolean(i);
        }

        public override byte GetByte(int i)
        {
            return Reader.GetByte(i);
        }

        public override long GetBytes(int i, long fieldOffset, byte[] buffer, int bufferoffset, int length)
        {
            return Reader.GetBytes(i, fieldOffset, buffer, bufferoffset, length);
        }

        public override char GetChar(int i)
        {
            return Reader.GetChar(i);
        }

        public override long GetChars(int i, long fieldoffset, char[] buffer, int bufferoffset, int length)
        {
            return Reader.GetChars(i, fieldoffset, buffer, bufferoffset, length);
        }

        protected override IDataReader GetDbDataReader(int ordinal)
        {
            return Reader.GetData(ordinal);
        }

        public override string GetDataTypeName(int i)
        {
            return Reader.GetDataTypeName(i);
        }

        public override DateTime GetDateTime(int i)
        {
            return Reader.GetDateTime(i);
        }

        public override decimal GetDecimal(int i)
        {
            return Reader.GetDecimal(i);
        }

        public override double GetDouble(int i)
        {
            return Reader.GetDouble(i);
        }

        public override Type GetFieldType(int i)
        {
            return Reader.GetFieldType(i);
        }

        public override float GetFloat(int i)
        {
            return Reader.GetFloat(i);
        }

        public override Guid GetGuid(int i)
        {
            return Reader.GetGuid(i);
        }

        public override short GetInt16(int i)
        {
            return Reader.GetInt16(i);
        }

        public override int GetInt32(int i)
        {
            return Reader.GetInt32(i);
        }

        public override long GetInt64(int i)
        {
            return Reader.GetInt64(i);
        }

        public override string GetName(int i)
        {
            return Reader.GetName(i);
        }

        public override int GetOrdinal(string name)
        {
            return Reader.GetOrdinal(name);
        }

        public override string GetString(int i)
        {
            return Reader.GetString(i);
        }

        public override object GetValue(int i)
        {
            return Reader.GetValue(i);
        }

        public override int GetValues(object[] values)
        {
            return Reader.GetValues(values);
        }

        public override bool IsDBNull(int i)
        {
            return Reader.IsDBNull(i);
        }

        public override object this[string name]
        {
            get { return Reader[name]; }
        }

        public override object this[int i]
        {
            get { return Reader[i]; }
        }
    }
#else

    internal class WrappedReader : IDataReader, IWrappedDataReader
    {
        private IDataReader reader;
        private IDbCommand cmd;

        public IDataReader Reader
        {
            get
            {
                var tmp = reader;
                if (tmp == null) throw new ObjectDisposedException(GetType().Name);
                return tmp;
            }
        }
        IDbCommand IWrappedDataReader.Command
        {
            get
            {
                var tmp = cmd;
                if (tmp == null) throw new ObjectDisposedException(GetType().Name);
                return tmp;
            }
        }
        public WrappedReader(IDbCommand cmd, IDataReader reader)
        {
            this.cmd = cmd;
            this.reader = reader;
        }

        void IDataReader.Close()
        {
            if(reader != null) reader.Close();
        }

        int IDataReader.Depth
        {
            get { return Reader.Depth; }
        }

        DataTable IDataReader.GetSchemaTable()
        {
            return Reader.GetSchemaTable();
        }

        bool IDataReader.IsClosed
        {
            get { return reader == null ? true : reader.IsClosed; }
        }

        bool IDataReader.NextResult()
        {
            return Reader.NextResult();
        }

        bool IDataReader.Read()
        {
            return Reader.Read();
        }

        int IDataReader.RecordsAffected
        {
            get { return Reader.RecordsAffected; }
        }

        void IDisposable.Dispose()
        {
            if (reader != null) reader.Close();
            if (reader != null) reader.Dispose();
            reader = null;
            if (cmd != null) cmd.Dispose();
            cmd = null;
        }

        int IDataRecord.FieldCount
        {
            get { return Reader.FieldCount; }
        }

        bool IDataRecord.GetBoolean(int i)
        {
            return Reader.GetBoolean(i);
        }

        byte IDataRecord.GetByte(int i)
        {
            return Reader.GetByte(i);
        }

        long IDataRecord.GetBytes(int i, long fieldOffset, byte[] buffer, int bufferoffset, int length)
        {
            return Reader.GetBytes(i, fieldOffset, buffer, bufferoffset, length);
        }

        char IDataRecord.GetChar(int i)
        {
            return Reader.GetChar(i);
        }

        long IDataRecord.GetChars(int i, long fieldoffset, char[] buffer, int bufferoffset, int length)
        {
            return Reader.GetChars(i, fieldoffset, buffer, bufferoffset, length);
        }

        IDataReader IDataRecord.GetData(int i)
        {
            return Reader.GetData(i);
        }

        string IDataRecord.GetDataTypeName(int i)
        {
            return Reader.GetDataTypeName(i);
        }

        DateTime IDataRecord.GetDateTime(int i)
        {
            return Reader.GetDateTime(i);
        }

        decimal IDataRecord.GetDecimal(int i)
        {
            return Reader.GetDecimal(i);
        }

        double IDataRecord.GetDouble(int i)
        {
            return Reader.GetDouble(i);
        }

        Type IDataRecord.GetFieldType(int i)
        {
            return Reader.GetFieldType(i);
        }

        float IDataRecord.GetFloat(int i)
        {
            return Reader.GetFloat(i);
        }

        Guid IDataRecord.GetGuid(int i)
        {
            return Reader.GetGuid(i);
        }

        short IDataRecord.GetInt16(int i)
        {
            return Reader.GetInt16(i);
        }

        int IDataRecord.GetInt32(int i)
        {
            return Reader.GetInt32(i);
        }

        long IDataRecord.GetInt64(int i)
        {
            return Reader.GetInt64(i);
        }

        string IDataRecord.GetName(int i)
        {
            return Reader.GetName(i);
        }

        int IDataRecord.GetOrdinal(string name)
        {
            return Reader.GetOrdinal(name);
        }

        string IDataRecord.GetString(int i)
        {
            return Reader.GetString(i);
        }

        object IDataRecord.GetValue(int i)
        {
            return Reader.GetValue(i);
        }

        int IDataRecord.GetValues(object[] values)
        {
            return Reader.GetValues(values);
        }

        bool IDataRecord.IsDBNull(int i)
        {
            return Reader.IsDBNull(i);
        }

        object IDataRecord.this[string name]
        {
            get { return Reader[name]; }
        }

        object IDataRecord.this[int i]
        {
            get { return Reader[i]; }
        }
    }
#endif

#if DNXCORE50
    /// <summary>
    /// Describes a reader that controls the lifetime of both a command and a reader,
    /// exposing the downstream command/reader as properties.
    /// </summary>
    public abstract class WrappedDataReader : IDataReader
    {
        /// <summary>
        /// Obtain the underlying reader
        /// </summary>
        public abstract IDataReader Reader { get; }
        /// <summary>
        /// Obtain the underlying command
        /// </summary>
        public abstract IDbCommand Command { get; }
    }
#else
    /// <summary>
    /// Describes a reader that controls the lifetime of both a command and a reader,
    /// exposing the downstream command/reader as properties.
    /// </summary>
    public interface IWrappedDataReader : IDataReader
    {
        /// <summary>
        /// Obtain the underlying reader
        /// </summary>
        IDataReader Reader { get; }
        /// <summary>
        /// Obtain the underlying command
        /// </summary>
        IDbCommand Command { get; }
    }
#endif

    /// <summary>
    /// Tell Dapper to use an explicit constructor, passing nulls or 0s for all parameters
    /// </summary>
    [AttributeUsage(AttributeTargets.Constructor, AllowMultiple = false)]
    public sealed class ExplicitConstructorAttribute : Attribute
    {

    }

    // Define DAPPER_MAKE_PRIVATE if you reference Dapper by source
    // and you like to make the Dapper types private (in order to avoid
    // conflicts with other projects that also reference Dapper by source)
#if !DAPPER_MAKE_PRIVATE

    public partial class SqlMapper
    {
    }

    public partial class DynamicParameters
    {

    }

    public partial class DbString
    {

    }

    
    public partial class SimpleMemberMap
    {

    }

    public partial class DefaultTypeMap
    {

    }

    public partial class CustomPropertyTypeMap
    {

    }

    public partial class FeatureSupport
    {

    }

#endif

    internal static class TypeExtensions
    {
        public static bool IsValueType(this Type type)
        {
#if DNXCORE50
            return typeof(ValueType).IsAssignableFrom(type) && type != typeof(ValueType);
#else
            return type.IsValueType;
#endif
        }
        public static bool IsEnum(this Type type)
        {
#if DNXCORE50
            return typeof(Enum).IsAssignableFrom(type) && type != typeof(Enum);
#else
            return type.IsEnum;
#endif
        }
#if DNXCORE50
        public static TypeCode GetTypeCode(Type type)
        {
            if (type == null) return TypeCode.Empty;
            TypeCode result;
            if (typeCodeLookup.TryGetValue(type, out result)) return result;

            if (type.IsEnum())
            {
                type = Enum.GetUnderlyingType(type);
                if (typeCodeLookup.TryGetValue(type, out result)) return result;
            }
            return TypeCode.Object;
        }
        static readonly Dictionary<Type, TypeCode> typeCodeLookup = new Dictionary<Type, TypeCode>
        {
            {typeof(bool), TypeCode.Boolean },
            {typeof(byte), TypeCode.Byte },
            {typeof(char), TypeCode.Char},
            {typeof(DateTime), TypeCode.DateTime},
            {typeof(decimal), TypeCode.Decimal},
            {typeof(double), TypeCode.Double },
            {typeof(short), TypeCode.Int16 },
            {typeof(int), TypeCode.Int32 },
            {typeof(long), TypeCode.Int64 },
            {typeof(object), TypeCode.Object},
            {typeof(sbyte), TypeCode.SByte },
            {typeof(float), TypeCode.Single },
            {typeof(string), TypeCode.String },
            {typeof(ushort), TypeCode.UInt16 },
            {typeof(uint), TypeCode.UInt32 },
            {typeof(ulong), TypeCode.UInt64 },
        };
#else
        public static TypeCode GetTypeCode(Type type)
        {
            return Type.GetTypeCode(type);
        }
#endif
        public static MethodInfo GetPublicInstanceMethod(this Type type, string name, Type[] types)
        {
#if DNXCORE50
            var method = type.GetMethod(name, types);
            return (method != null && method.IsPublic && !method.IsStatic) ? method : null;
#else
            return type.GetMethod(name, BindingFlags.Instance | BindingFlags.Public, null, types, null);
#endif
        }


    }
}
