Map string to guid with Dapper

Question

I\'m using Dapper to hammer out some load testing tools that need to access a PostgreSQL database. This particular version of PostgreSQL does not support GUIDs natively, so

Answer 1

I hacked a solution together. As far as I can tell, there is no way to instruct Dapper to generate alternate binding code for a particular type so I modified the GetClassDeserializer method to force the unbox type to string if the property is a guid. Next I re-used the code that generates a constructor call for enums.

Here's the modified code snippet (starting at line 761 of rev. rf6d62f91f31a) :

// unbox nullable enums as the primitive, i.e. byte etc
  var nullUnderlyingType = Nullable.GetUnderlyingType( item.Info.Type );
  var unboxType = nullUnderlyingType != null && nullUnderlyingType.IsEnum ? nullUnderlyingType : item.Info.Type;
  if( unboxType == typeof(Guid))
  {
    unboxType = typeof (string);
  }
  il.Emit( OpCodes.Unbox_Any, unboxType ); // stack is now [target][target][typed-value]
  if (  ( item.Info.Type == typeof( Guid ) && unboxType == typeof( string ) ) 
        || ( nullUnderlyingType != null && nullUnderlyingType.IsEnum ) )
  {
    il.Emit( OpCodes.Newobj, item.Info.Type.GetConstructor( new[] { nullUnderlyingType ?? unboxType} ) );
  }

  il.Emit( OpCodes.Callvirt, item.Info.Setter ); // stack is now [target]