KunzeAndreas

@Yozer Yes, I am sure. The test ist running in Visual Studio. Maybe there is a difference between .Net and mono?  in dotPeek I see this private static void...

private static void FunctionWithOptionalParams(ref TestStruct structParam, ref decimal decimalParam, ref string strParam, ref DateTime dateParam) would break VB code calling converted C# code (in VB you can omit optional ref...

Optional ByRef xxx As Short = 0S converts to [Optional, DefaultParameterValue(0)] out short xxx should be [Optional, DefaultParameterValue((short)0)] out short xxx