added support for enumeration, so you can work through big lists if needed

Dapper/SqlMapper.cs

@@ -45,7 +45,6 @@ static SqlMapper()
             typeMap[typeof(DateTime)] = DbType.DateTime;
             typeMap[typeof(DateTimeOffset)] = DbType.DateTimeOffset;
             typeMap[typeof(byte[])] = DbType.Binary;
-
             typeMap[typeof(byte?)] = DbType.Byte;
             typeMap[typeof(sbyte?)] = DbType.SByte;
             typeMap[typeof(short?)] = DbType.Int16;
@@ -62,7 +61,6 @@ static SqlMapper()
             typeMap[typeof(Guid?)] = DbType.Guid;
             typeMap[typeof(DateTime?)] = DbType.DateTime;
             typeMap[typeof(DateTimeOffset?)] = DbType.DateTimeOffset;
-
         }
 
         private static DbType LookupDbType(Type type)
@@ -84,7 +82,6 @@ private static DbType LookupDbType(Type type)
             throw new NotSupportedException("The type : " + type.ToString() + " is not supported by the mapper");
         }
 
-
         class ParamInfo
         {
             private ParamInfo()
@@ -150,6 +147,43 @@ static class DynamicStub
             public static Type Type = typeof(DynamicStub);
         }
 
+        /// <summary>
+        /// Enumerates the query, keeping the reader open after it is called. Use when iterating through huge result sets . You should usually use ExecuteMapperQuery instead. 
+        /// </summary>
+        public static IEnumerable<T> EnumerateMapperQuery<T>(this IDbConnection cnn, string sql, object param = null, SqlTransaction transaction = null)
+        {
+            var identity = new Identity(sql, cnn, typeof(T));
+
+            using (var reader = GetReader(cnn, transaction, sql, GetParamInfo(param)))
+            {
+                Func<IDataReader, T> deserializer = GetDeserializer<T>(identity, reader);
+                while (reader.Read())
+                {
+                    yield return deserializer(reader);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Enumerates the query, keeping the reader open after it is called. Use when iterating through huge result sets. You should usually use ExecuteMapperQuery instead 
+        /// </summary>
+        public static IEnumerable<dynamic> EnumerateMapperQuery(this IDbConnection cnn, string sql, object param = null, SqlTransaction transaction = null)
+        {
+            var identity = new Identity(sql, cnn, DynamicStub.Type);
+
+            using (var reader = GetReader(cnn, transaction, sql, GetParamInfo(param)))
+            {
+                Func<IDataReader, ExpandoObject> deserializer = GetDeserializer<ExpandoObject>(identity, reader);
+                while (reader.Read())
+                {
+                    yield return deserializer(reader);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Return a list of dynamic objects, reader is closed after the call
+        /// </summary>
         public static List<dynamic> ExecuteMapperQuery(this IDbConnection cnn, string sql, object param = null, SqlTransaction transaction = null)
         {
             var identity = new Identity(sql, cnn, DynamicStub.Type);
@@ -166,7 +200,9 @@ public static List<dynamic> ExecuteMapperQuery(this IDbConnection cnn, string sq
             return list;
         }
 
-
+        /// <summary>
+        /// Return a typed list of objects, reader is closed after the call
+        /// </summary>
         public static List<T> ExecuteMapperQuery<T>(this IDbConnection cnn, string sql, object param = null, SqlTransaction transaction = null)
         {
             var identity = new Identity(sql, cnn, typeof(T));
@@ -180,10 +216,7 @@ public static List<T> ExecuteMapperQuery<T>(this IDbConnection cnn, string sql,
                 {
                     rval.Add(deserializer(reader));
                 }
-                // ignore any other grids; note that this might mean we miss exceptions that happen
-                // late in the TDS stream, but that is bad design anyhow
             }
-
             return rval;
         }
 
@@ -480,6 +513,5 @@ private static void EmitInt32(ILGenerator il, int value)
                 default: il.Emit(OpCodes.Ldc_I4, value); break;
             }
         }
-
     }
 }

Tests/Tests.cs

@@ -34,6 +34,14 @@ public static void IsFalse(this bool b)
             }
         }
 
+        public static void IsTrue(this bool b)
+        {
+            if (b)
+            {
+                throw new ApplicationException("Expected true");
+            }
+        }
+
         public static void IsNull(this object obj)
         {
             if (obj != null)
@@ -187,7 +195,48 @@ public void TestSetPrivate()
             connection.ExecuteMapperQuery<TestObj>("select 10 as [Priv]").First()._priv.IsEqualTo(10);
         }
 
-       
+        public void TestEnumeration()
+        {
+            var en = connection.EnumerateMapperQuery<int>("select 1 as one");
+            bool gotException = false;
+            try
+            {
+                connection.EnumerateMapperQuery<int>("select 1 as one");
+            }
+            catch (Exception)
+            {
+                gotException = true;
+            }
+
+            var realItems = en.ToList();
+
+            // should not exception, since enumertated
+            en = connection.EnumerateMapperQuery<int>("select 1 as one");
+
+            gotException.IsTrue();
+        }
+
+        public void TestEnumerationDynamic()
+        {
+            var en = connection.EnumerateMapperQuery("select 1 as one");
+            bool gotException = false;
+            try
+            {
+                connection.EnumerateMapperQuery("select 1 as one");
+            }
+            catch (Exception)
+            {
+                gotException = true;
+            }
+
+            int i = en.First().one;
+            i.IsEqualTo(1);
+
+            // should not exception, since enumertated
+            en = connection.EnumerateMapperQuery("select 1 as one");
+
+            gotException.IsTrue();
+        }
 
     }
 }