Error while converting VC++ code to C#

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OneDll.h

C++

typedef int (WINAPI *PFCALLBACK)(int Param1,char * Param2);
extern   "C"   __declspec(dllexport)   void   WINAPI   CallBack(PFCALLBACK   Func);

DemoDlg.cpp

C++

CallBack(ProcessCallBackMessage);
int WINAPI ProcessCallBackMessage(int Param1,char *Param2)
{
	if(m_DlgWnd==NULL)
        return 0;
	::PostMessage(m_DlgWnd,WM_MSG_DLG_WND,Param1,(LPARAM)Param2);
	return 0;
}

how can I write Same in C#???

and this is what i've tried to do....

C#

 public delegate void CALLBACK_PROC(int iType, char * buffer);
       CALLBACK_PROC myCallbackFunc = new CALLBACK_PROC(ProcessCallBackMessage);

public static void ProcessCallBackMessage(int iType, String buffer)
        {
            //string strIp = Marshal.PtrToStringAnsi((IntPtr)buffer, 2000);
            int h1 =(int) sIntHandle;//0;
            
            h1 = FindWindow(null, "LedSign");
            if (h1 != 0)
                SendMessage(h1, 2000, iType, (IntPtr)buffer);
        }

But this doesn't seem to work....

Posted 18-Jun-13 19:21pm

Sharath2790

Updated 18-Jun-13 19:54pm

v3

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2 solutions

Solution 1

This is not C++, it's WinAPI calls IN C++. You need to work out what this code was doing and find how to do it in C#, there's no direct conversion code, because the API is different. Even p/invoke won't help here, I don't think. Callback functions are easy in C#, those are delegates, but that does not help, really.

Posted 18-Jun-13 19:51pm

Christian Graus

Comments

johannesnestler 19-Jun-13 10:32am

In general I agree - but for the code shown by OP I'd use p/invoke for the API-Functions (FindWindow, SendMessage) and just re-wrap the calls from C#. But if he is willing to do that (I assume he has more code than showed), he may also just call the existing C++ library and use interop... Porting code - always fun :-(

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Pascal-78 · Accepted Answer · 2013-06-24T04:20:00

You should get a look at:
Marshal.GetFunctionPointerForDelegate Method

May be you can declare your delegate like this:

C#

public delegate void TheCallbackDelegate(int iType, String buffer);

And call the dll method (declared with p/invoke) :

C#

Callback(Marshal.GetFunctionPointerForDelegate(new TheCallbackDelegate(ProcessCallbackMessage)));