Added method to use AnsiString as Default

Dapper NET40/SqlMapper.cs

@@ -2002,7 +2002,7 @@ private static IEnumerable<PropertyInfo> FilterParameters(IEnumerable<PropertyIn
                 }
                 if (checkForNull)
                 {
-                    if (dbType == DbType.String && !haveInt32Arg1)
+                    if ((dbType == DbType.String || dbType == DbType.AnsiString) && !haveInt32Arg1)
                     {
                         il.DeclareLocal(typeof(int));
                         haveInt32Arg1 = true;
@@ -2010,12 +2010,12 @@ private static IEnumerable<PropertyInfo> FilterParameters(IEnumerable<PropertyIn
                     // relative stack: [boxed value]
                     il.Emit(OpCodes.Dup);// relative stack: [boxed value] [boxed value]
                     Label notNull = il.DefineLabel();
-                    Label? allDone = dbType == DbType.String ? il.DefineLabel() : (Label?)null;
+                    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)
+                    if (dbType == DbType.String || dbType == DbType.AnsiString)
                     {
                         EmitInt32(il, 0);
                         il.Emit(OpCodes.Stloc_1);

Tests/Tests.cs

@@ -2505,6 +2505,24 @@ public void TestNullFromInt_NoRows()
 
         }
 
+        public void TestChangingDefaultStringTypeMappingToAnsiString()
+        {
+            var sql = "SELECT SQL_VARIANT_PROPERTY(CONVERT(sql_variant, @testParam),'BaseType') AS BaseType";
+            var param = new {testParam = "TestString"};
+
+            var result01 = connection.Query<string>(sql, param).FirstOrDefault();
+            result01.IsEqualTo("nvarchar");
+
+            Dapper.SqlMapper.PurgeQueryCache();
+
+            Dapper.SqlMapper.AddTypeMap(typeof(string), DbType.AnsiString);   // Change Default String Handling to AnsiString
+            var result02 = connection.Query<string>(sql, param).FirstOrDefault();
+            result02.IsEqualTo("varchar");
+
+            Dapper.SqlMapper.PurgeQueryCache();
+            Dapper.SqlMapper.AddTypeMap(typeof(string), DbType.String);  // Restore Default to Unicode String
+        }
+
         class TransactedConnection : IDbConnection
         {
             IDbConnection _conn;