Interfaces are back, simplifying code.

Related issue: #520

Dapper.Contrib/SqlMapperExtensions.Async.cs

 #if ASYNC
 using System;
 using System.Collections.Generic;
+using System.Data;
 using System.Linq;
 using System.Reflection;
 using System.Text;
 using System.Threading.Tasks;
 using Dapper;
 
-#if COREFX
-using IDbTransaction = System.Data.Common.DbTransaction;
-using IDbConnection = System.Data.Common.DbConnection;
-using DataException = System.InvalidOperationException;
-#else
-using System.Data;
-#endif
 
 namespace Dapper.Contrib.Extensions
 {

Dapper.Contrib/SqlMapperExtensions.cs

@@ -10,8 +10,6 @@
 using Dapper;
 
 #if COREFX
-using IDbTransaction = System.Data.Common.DbTransaction;
-using IDbConnection = System.Data.Common.DbConnection;
 using DataException = System.InvalidOperationException;
 #else
 using System.Threading;

Dapper.Rainbow/Database.Async.cs

@@ -6,10 +6,6 @@
 using System.Text;
 using System.Threading.Tasks;
 
-#if COREFX
-using IDbTransaction = System.Data.Common.DbTransaction;
-#endif
-
 namespace Dapper
 {
     public abstract partial class Database<TDatabase> where TDatabase : Database<TDatabase>, new()

Dapper.Rainbow/Database.cs

@@ -8,10 +8,6 @@
 using System.Data.Common;
 using System.Reflection.Emit;
 
-#if COREFX
-using IDbTransaction = System.Data.Common.DbTransaction;
-#endif
-
 namespace Dapper
 {
     /// <summary>

Dapper.Tests.Contrib/TestSuite.cs

@@ -5,10 +5,7 @@
 
 using Dapper.Contrib.Extensions;
 
-#if COREFX
-using System.Reflection;
-using IDbConnection = System.Data.Common.DbConnection;
-#else
+#if !COREFX
 using System.Data.SqlServerCe;
 using System.Transactions;
 #endif

Dapper.Tests.Contrib/TestSuites.cs

@@ -6,7 +6,6 @@
 using Xunit.Sdk;
 #if COREFX
 using Microsoft.Data.Sqlite;
-using IDbConnection = System.Data.Common.DbConnection;
 #else
 using System.Data.SQLite;
 using System.Data.SqlServerCe;

Dapper.Tests/Tests.Async.cs

@@ -8,10 +8,6 @@
 using System.Data.SqlClient;
 using Xunit;
 
-#if COREFX
-using IDbConnection = System.Data.Common.DbConnection;
-#endif
-
 namespace Dapper.Tests
 {
     public partial class TestSuite

Dapper.Tests/Tests.Constructors.cs

@@ -4,14 +4,6 @@
 using System.Linq;
 using Xunit;
 
-#if COREFX
-using IDbCommand = System.Data.Common.DbCommand;
-using IDbDataParameter = System.Data.Common.DbParameter;
-using IDbConnection = System.Data.Common.DbConnection;
-using IDbTransaction = System.Data.Common.DbTransaction;
-using IDataReader = System.Data.Common.DbDataReader;
-#endif
-
 namespace Dapper.Tests
 {
     public partial class TestSuite

Dapper.Tests/Tests.Enums.cs

@@ -4,14 +4,6 @@
 using System.Linq;
 using Xunit;
 
-#if COREFX
-using IDbCommand = System.Data.Common.DbCommand;
-using IDbDataParameter = System.Data.Common.DbParameter;
-using IDbConnection = System.Data.Common.DbConnection;
-using IDbTransaction = System.Data.Common.DbTransaction;
-using IDataReader = System.Data.Common.DbDataReader;
-#endif
-
 namespace Dapper.Tests
 {
     public partial class TestSuite

Dapper.Tests/Tests.MultiMap.cs

@@ -5,14 +5,6 @@
 using System.Linq;
 using Xunit;
 
-#if COREFX
-using IDbCommand = System.Data.Common.DbCommand;
-using IDbDataParameter = System.Data.Common.DbParameter;
-using IDbConnection = System.Data.Common.DbConnection;
-using IDbTransaction = System.Data.Common.DbTransaction;
-using IDataReader = System.Data.Common.DbDataReader;
-#endif
-
 namespace Dapper.Tests
 {
     public partial class TestSuite

Dapper.Tests/Tests.Parameters.cs

@@ -14,14 +14,6 @@
 using Microsoft.SqlServer.Types;
 #endif
 
-#if COREFX
-using IDbCommand = System.Data.Common.DbCommand;
-using IDbDataParameter = System.Data.Common.DbParameter;
-using IDbConnection = System.Data.Common.DbConnection;
-using IDbTransaction = System.Data.Common.DbTransaction;
-using IDataReader = System.Data.Common.DbDataReader;
-#endif
-
 namespace Dapper.Tests
 {
     public partial class TestSuite

Dapper.Tests/Tests.QueryMultiple.cs

@@ -4,14 +4,6 @@
 using System.Linq;
 using Xunit;
 
-#if COREFX
-using IDbCommand = System.Data.Common.DbCommand;
-using IDbDataParameter = System.Data.Common.DbParameter;
-using IDbConnection = System.Data.Common.DbConnection;
-using IDbTransaction = System.Data.Common.DbTransaction;
-using IDataReader = System.Data.Common.DbDataReader;
-#endif
-
 namespace Dapper.Tests
 {
     public partial class TestSuite
@@ -48,7 +40,6 @@ public void TestQueryMultipleNonBufferedIncorrectOrder()
                 {
                     // that's expected
                 }
-
             }
         }
 

Dapper.Tests/Tests.cs

 //#define POSTGRESQL // uncomment to run postgres tests
 
-#if COREFX
-using IDbCommand = System.Data.Common.DbCommand;
-using IDbDataParameter = System.Data.Common.DbParameter;
-using IDbConnection = System.Data.Common.DbConnection;
-using IDbTransaction = System.Data.Common.DbTransaction;
-using IDataReader = System.Data.Common.DbDataReader;
-#endif
-
 #if SQLITE && (NET40 || NET45)
 using SqliteConnection = System.Data.SQLite.SQLiteConnection;
 #endif
@@ -1847,60 +1839,6 @@ public void TestChangingDefaultStringTypeMappingToAnsiStringFirstOrDefault()
             Dapper.SqlMapper.AddTypeMap(typeof(string), DbType.String);  // Restore Default to Unicode String
         }
 
-#if COREFX
-        class TransactedConnection : IDbConnection
-        {
-            IDbConnection _conn;
-            IDbTransaction _tran;
-
-            public TransactedConnection(IDbConnection conn, IDbTransaction tran)
-            {
-                _conn = conn;
-                _tran = tran;
-            }
-
-            public override string ConnectionString { get { return _conn.ConnectionString; } set { _conn.ConnectionString = value; } }
-            public override int ConnectionTimeout => _conn.ConnectionTimeout;
-            public override string Database => _conn.Database;
-            public override ConnectionState State => _conn.State;
-
-            protected override IDbTransaction BeginDbTransaction(IsolationLevel isolationLevel)
-            {
-                return _tran;
-            }
-            
-            public override void ChangeDatabase(string databaseName)
-            {
-                _conn.ChangeDatabase(databaseName);
-            }
-            public override string DataSource => _conn.DataSource;
-
-            public override string ServerVersion => _conn.ServerVersion;
-
-            public override void Close()
-            {
-                _conn.Close();
-            }
-            protected override IDbCommand CreateDbCommand()
-            {
-                // The command inherits the "current" transaction.
-                var command = _conn.CreateCommand();
-                command.Transaction = _tran;
-                return command;
-            }
-
-            protected override void Dispose(bool disposing)
-            {
-                if(disposing) _conn.Dispose();
-                base.Dispose(disposing);
-            }
-
-            public override void Open()
-            {
-                _conn.Open();
-            }
-        }
-#else
         class TransactedConnection : IDbConnection
         {
             IDbConnection _conn;
@@ -1955,7 +1893,6 @@ public void Open()
                 _conn.Open();
             }
         }
-#endif
 
         [Fact]
         public void TestDapperTableMetadataRetrieval()

Dapper/CommandDefinition.cs

@@ -4,12 +4,6 @@
 using System.Reflection.Emit;
 using System.Threading;
 
-#if COREFX
-using IDbTransaction = System.Data.Common.DbTransaction;
-using IDbConnection = System.Data.Common.DbConnection;
-using IDbCommand = System.Data.Common.DbCommand;
-#endif
-
 namespace Dapper
 {
     /// <summary>

Dapper/DbString.cs

 using System;
 using System.Data;
 
-#if COREFX
-using IDbCommand = System.Data.Common.DbCommand;
-#endif
-
 namespace Dapper
 {
     /// <summary>

Dapper/DefaultTypeMap.cs

@@ -195,6 +195,9 @@ public SqlMapper.IMemberMap GetMember(string columnName)
         /// </summary>
         public static bool MatchNamesWithUnderscores { get; set; }
 
+        /// <summary>
+        /// The settable properties for this typemap
+        /// </summary>
         public List<PropertyInfo> Properties { get; }
     }
 }

Dapper/DynamicParameters.ParamInfo.cs

 using System;
 using System.Data;
 
-#if COREFX
-using IDbDataParameter = System.Data.Common.DbParameter;
-#endif
 namespace Dapper
 {
     partial class DynamicParameters

Dapper/DynamicParameters.cs

@@ -7,8 +7,6 @@
 using System.Reflection.Emit;
 
 #if COREFX
-using IDbDataParameter = System.Data.Common.DbParameter;
-using IDbCommand = System.Data.Common.DbCommand;
 using ApplicationException = System.InvalidOperationException;
 #endif
 

Dapper/FeatureSupport.cs

 using System;
 using System.Data;
 
-#if COREFX
-using IDbConnection = System.Data.Common.DbConnection;
-#endif
 namespace Dapper
 {
     /// <summary>

Dapper/SqlMapper.Async.cs

@@ -9,13 +9,6 @@
 using System.Threading;
 using System.Threading.Tasks;
 
-#if COREFX
-using IDbTransaction = System.Data.Common.DbTransaction;
-using IDbConnection = System.Data.Common.DbConnection;
-using IDbCommand = System.Data.Common.DbCommand;
-using IDataReader = System.Data.Common.DbDataReader;
-#endif
-
 namespace Dapper
 {
     public static partial class SqlMapper

Dapper/SqlMapper.CacheInfo.cs

@@ -2,11 +2,6 @@
 using System.Data;
 using System.Threading;
 
-#if COREFX
-using IDbCommand = System.Data.Common.DbCommand;
-using IDataReader = System.Data.Common.DbDataReader;
-#endif
-
 namespace Dapper
 {
     partial class SqlMapper

Dapper/SqlMapper.DeserializerState.cs

 using System;
 using System.Data;
 
-#if COREFX
-using IDataReader = System.Data.Common.DbDataReader;
-#endif
-
 namespace Dapper
 {
     partial class SqlMapper

Dapper/SqlMapper.GridReader.Async.cs

@@ -6,10 +6,7 @@
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
-#if COREFX
-using IDbCommand = System.Data.Common.DbCommand;
-using IDataReader = System.Data.Common.DbDataReader;
-#endif
+
 namespace Dapper
 {
     partial class SqlMapper

Dapper/SqlMapper.GridReader.cs

@@ -3,11 +3,6 @@
 using System.Data;
 using System.Linq;
 
-#if COREFX
-using IDbCommand = System.Data.Common.DbCommand;
-using IDataReader = System.Data.Common.DbDataReader;
-#endif
-
 namespace Dapper
 {
     partial class SqlMapper

Dapper/SqlMapper.ICustomQueryParameter.cs

 using System.Data;
 
-#if COREFX
-using IDbCommand = System.Data.Common.DbCommand;
-#endif
 namespace Dapper
 {
     partial class SqlMapper

Dapper/SqlMapper.IDataReader.cs

@@ -2,10 +2,6 @@
 using System.Collections.Generic;
 using System.Data;
 
-#if COREFX
-using IDataReader = System.Data.Common.DbDataReader;
-#endif
-
 namespace Dapper
 {
     partial class SqlMapper

Dapper/SqlMapper.IDynamicParameters.cs

 using System.Data;
 
-#if COREFX
-using IDbCommand = System.Data.Common.DbCommand;
-#endif
-
 namespace Dapper
 {
     partial class SqlMapper

Dapper/SqlMapper.ITypeHandler.cs

 using System;
 using System.Data;
 
-#if COREFX
-using IDbDataParameter = System.Data.Common.DbParameter;
-#endif
 namespace Dapper
 {
     partial class SqlMapper

Dapper/SqlMapper.Identity.cs

 using System;
 using System.Data;
 
-#if COREFX
-using IDbConnection = System.Data.Common.DbConnection;
-#endif
-
 namespace Dapper
 {
     partial class SqlMapper

Dapper/SqlMapper.TypeDeserializerCache.cs

-#if COREFX
-using IDataReader = System.Data.Common.DbDataReader;
-#endif
-
-using System;
+using System;
 using System.Data;
 using System.Collections;
 using System.Collections.Generic;

Dapper/SqlMapper.TypeHandler.cs

 using System;
 using System.Data;
 
-#if COREFX
-using IDbDataParameter = System.Data.Common.DbParameter;
-#endif
-
 namespace Dapper
 {
     partial class SqlMapper

Dapper/SqlMapper.TypeHandlerCache.cs

@@ -2,10 +2,6 @@
 using System.ComponentModel;
 using System.Data;
 
-#if COREFX
-using IDbDataParameter = System.Data.Common.DbParameter;
-#endif
-
 namespace Dapper
 {
     partial class SqlMapper

Dapper/SqlMapper.cs

@@ -3,18 +3,6 @@
  Home page: https://github.com/StackExchange/dapper-dot-net
  */
 
-#if COREFX
-using IDbDataParameter = System.Data.Common.DbParameter;
-using IDataParameter = System.Data.Common.DbParameter;
-using IDbTransaction = System.Data.Common.DbTransaction;
-using IDbConnection = System.Data.Common.DbConnection;
-using IDbCommand = System.Data.Common.DbCommand;
-using IDataReader = System.Data.Common.DbDataReader;
-using IDataRecord = System.Data.Common.DbDataReader;
-using IDataParameterCollection = System.Data.Common.DbParameterCollection;
-using DataException = System.InvalidOperationException;
-#endif
-
 using System;
 using System.Collections;
 using System.Collections.Generic;
@@ -31,6 +19,10 @@
 using System.Xml;
 using System.Xml.Linq;
 
+#if COREFX
+using DataException = System.InvalidOperationException;
+#endif
+
 namespace Dapper
 {
 

Dapper/WrappedDataReader.cs

 using System.Data;
 
-#if COREFX
-using IDbCommand = System.Data.Common.DbCommand;
-using IDataReader = System.Data.Common.DbDataReader;
-#endif
-
 namespace Dapper
 {
-#if COREFX
-    /// <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.
@@ -39,5 +17,4 @@ public interface IWrappedDataReader : IDataReader
         /// </summary>
         IDbCommand Command { get; }
     }
-#endif
 }

Dapper/WrappedReader.cs

 using System;
 using System.Data;
-using System.Collections;
-
-#if COREFX
-using IDbCommand = System.Data.Common.DbCommand;
-using IDataReader = System.Data.Common.DbDataReader;
-#endif
 
 namespace Dapper
 {
-#if COREFX
-    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(this.GetType().Name);
-                return tmp;
-            }
-        }
-        public override IDbCommand Command
-        {
-            get
-            {
-                var tmp = cmd;
-                if (tmp == null) throw new ObjectDisposedException(this.GetType().Name);
-                return tmp;
-            }
-        }
-
-        public override int Depth => Reader.Depth;
-
-        public override bool IsClosed => reader?.IsClosed ?? true;
-
-        public override bool HasRows => Reader.HasRows;
-
-        public override bool NextResult() => Reader.NextResult();
-
-        public override bool Read() => Reader.Read();
-
-        public override int RecordsAffected => Reader.RecordsAffected;
-
-
-        protected override void Dispose(bool disposing)
-        {
-            if (disposing)
-            {
-                reader?.Dispose();
-                reader = null;
-                cmd?.Dispose();
-                cmd = null;
-            }
-            base.Dispose(disposing);
-        }
-
-        public override int FieldCount => Reader.FieldCount;
-
-        public override bool GetBoolean(int i) => Reader.GetBoolean(i);
-
-        public override byte GetByte(int i) => 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) => 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) => Reader.GetData(ordinal);
-
-        public override string GetDataTypeName(int i) => Reader.GetDataTypeName(i);
-
-        public override DateTime GetDateTime(int i) => Reader.GetDateTime(i);
-
-        public override decimal GetDecimal(int i) => Reader.GetDecimal(i);
-
-        public override double GetDouble(int i) => Reader.GetDouble(i);
-
-        public override Type GetFieldType(int i) => Reader.GetFieldType(i);
-
-        public override float GetFloat(int i) => Reader.GetFloat(i);
-
-        public override Guid GetGuid(int i) => Reader.GetGuid(i);
-
-        public override short GetInt16(int i) => Reader.GetInt16(i);
-
-        public override int GetInt32(int i) => Reader.GetInt32(i);
-
-        public override long GetInt64(int i) => Reader.GetInt64(i);
-
-        public override string GetName(int i) => Reader.GetName(i);
-
-        public override int GetOrdinal(string name) => Reader.GetOrdinal(name);
-
-        public override string GetString(int i) => Reader.GetString(i);
-
-        public override object GetValue(int i) => Reader.GetValue(i);
-
-        public override int GetValues(object[] values) => Reader.GetValues(values);
-
-        public override bool IsDBNull(int i) => Reader.IsDBNull(i);
-
-        public override object this[string name] => Reader[name];
-
-        public override object this[int i] => Reader[i];
-    }
-#else
-
     internal class WrappedReader : IDataReader, IWrappedDataReader
     {
         private IDataReader reader;
@@ -306,5 +183,4 @@ bool IDataRecord.IsDBNull(int i)
 
         object IDataRecord.this[int i] => Reader[i];
     }
-#endif
 }

Dapper/XmlHandlers.cs

 using System.Data;
 using System.Xml;
 using System.Xml.Linq;
-#if COREFX
-using IDbDataParameter = System.Data.Common.DbParameter;
-#endif
 
 namespace Dapper
 {