Triggering event in C# from C++ DLL

Question

I have an umanaged C++ DLL which is communicating with a Cisco Server (UCCX).

It sends and receives messages to and from this server via TCP/IP. Now there are some types of messages it receives which contains some parameters which it needs to send to a C# GUI which will display these parameters on screen.

Please tell me an efficient method to trigger an event in C# from this DLL.

Answer 1

http://blogs.msdn.com/b/davidnotario/archive/2006/01/13/512436.aspx seems to answer your question. You use a delegate on the C# side and a standard callback on the C++ side.

C++ side:

typedef void (__stdcall *PFN_MYCALLBACK)();
int __stdcall MyUnmanagedApi(PFN_ MYCALLBACK callback);

C# side

public delegate void MyCallback();
[DllImport("MYDLL.DLL")] public static extern void MyUnmanagedApi(MyCallback callback);

public static void Main()
{
  MyUnmanagedApi(
    delegate()
    {
      Console.WriteLine("Called back by unmanaged side");
    }
   );
}

Answer 2

Note the C++ side should be

typedef void (__stdcall *PFN_MYCALLBACK)();
extern "C" __declspec(dllexport) void __stdcall MyUnmanagedApi(PFN_ MYCALLBACK callback);

An alternate option is to drop the __stdcall on the C++ side

typedef void (*PFN_MYCALLBACK)();
extern "C" __declspec(dllexport) void MyUnmanagedApi(PFN_ MYCALLBACK callback);

And on the C# side:

public delegate void MyCallback();
[DllImport("MYDLL.DLL", CallingConvention = CallingConvention.Cdecl))] 
public static extern void MyUnmanagedApi(MyCallback callback);

as above ...