C# calling C++ DLL: pass struct

Question

Hi, i am trying to call unmanaged C++ DLL in my C# application i converted all the structures to be .net compatible (e.g TCHAR to string (including Marshal As) one of the functions i try to call is defined in the DLL bool hhpConnect(Connection_tag* ptag, PTCHAR msg); where Connection_tag is defined as typedef Connection_tag { ...... } when i try to call it in C#, i use [DllImport("MyDLL.dll", CharSet=CharSet.Auto)] i am not sure how to call the Pointer to a structure? should i use public static extern bool hhpConnect([Ref, MarshalAs(UnmanagedType.Struct)] ref Connection_tag ptag,[MarshalAs(UnmanagedType.ByValTStr)] msg); i am confused, the *ptag would hold the connection setup parameters..? also, i think i need to MRashal the string msg too? how this be different if *ptag was to be changed in the hhpConnect? Thanks ALL Mo [email protected]