Implement connection-string equivalence (similar to...

Implement connection-string equivalence (similar to https://github.com/SamSaffron/dapper-dot-net/pull/80)

Fix Issue131

Dapper/SqlMapper.cs

@@ -494,7 +494,7 @@ private Identity(string sql, CommandType? commandType, string connectionString,
                             hashCode = hashCode * 23 + (t == null ? 0 : t.GetHashCode());
                         }
                     }
-                    hashCode = hashCode * 23 + (connectionString == null ? 0 : connectionString.GetHashCode());
+                    hashCode = hashCode * 23 + (connectionString == null ? 0 : SqlMapper.connectionStringComparer.GetHashCode(connectionString));
                     hashCode = hashCode * 23 + (parametersType == null ? 0 : parametersType.GetHashCode());
                 }
             }
@@ -554,7 +554,7 @@ public bool Equals(Identity other)
                     type == other.type &&
                     sql == other.sql &&
                     commandType == other.commandType &&
-                    connectionString == other.connectionString &&
+                    SqlMapper.connectionStringComparer.Equals(connectionString, other.connectionString) &&
                     parametersType == other.parametersType;
             }
         }
@@ -898,7 +898,7 @@ private static IEnumerable<T> QueryInternal<T>(this IDbConnection cnn, string sq
 #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, dynamic param = null, IDbTransaction transaction = null, bool buffered = true, string splitOn = "Id", int? commandTimeout = null, CommandType? commandType = null
+            this IDbConnection cnn, string sql, Func<TFirst, TSecond, TReturn> map, dynamic param = null, IDbTransaction transaction = null, bool buffered = true, string splitOn = "Id", int? commandTimeout = null, CommandType? commandType = null
 #endif
 )
         {
@@ -1519,7 +1519,7 @@ public object SetValue(string key, object value)
                 throw new ArgumentException("When using the multi-mapping APIs ensure you set the splitOn param if you have keys other than Id", "splitOn");
             }
 
-            var effectiveFieldCount = fieldCount - startBound;
+            var effectiveFieldCount = Math.Min(fieldCount - startBound, length);
 
             DapperTable table = null;
 
@@ -2477,6 +2477,20 @@ private static void EmitInt32(ILGenerator il, int value)
             }
         }
 
+
+        /// <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 startegies. 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>

Tests/Tests.cs

@@ -2211,6 +2211,41 @@ public void TestDynamicMutation()
             }
         }
 
+        public void TestIssue131()
+        {
+            var results = connection.Query<dynamic, int, dynamic>(
+                "SELECT 1 Id, 'Mr' Title, 'John' Surname, 4 AddressCount",
+                (person, addressCount) =>
+                {
+                    return person;
+                },
+                splitOn: "AddressCount"
+            ).FirstOrDefault();
+
+            var asDict = (IDictionary<string, object>)results;
+
+            asDict.ContainsKey("Id").IsEqualTo(true);
+            asDict.ContainsKey("Title").IsEqualTo(true);
+            asDict.ContainsKey("Surname").IsEqualTo(true);
+            asDict.ContainsKey("AddressCount").IsEqualTo(false);
+        }
+
+        // see http://stackoverflow.com/questions/13127886/dapper-returns-null-for-singleordefaultdatediff
+        public void TestNullFromInt_NoRows()
+        {
+            var result = connection.Query<int>( // case with rows
+             "select DATEDIFF(day, GETUTCDATE(), @date)", new { date = DateTime.UtcNow.AddDays(20) })
+             .SingleOrDefault();
+            result.IsEqualTo(20);
+
+            result = connection.Query<int>( // case without rows
+                "select DATEDIFF(day, GETUTCDATE(), @date) where 1 = 0", new { date = DateTime.UtcNow.AddDays(20) })
+                .SingleOrDefault();
+            result.IsEqualTo(0); // zero rows; default of int over zero rows is zero
+
+
+        }
+
         class TransactedConnection : IDbConnection
         {
             IDbConnection _conn;