MFC CWnd::CreateEx throws exception when the project is DLL, but runnig fine when exe

Question

I have a C++ gui application(MFC). I have made it dll and used its functionality from my C# windows exe application. Surely I'm not showing any window that previously were shown from C++ application.

For the following line i'm getting the error

Error: "Microsoft Visual C++ Debug Library... Debug Assertion Failed!... afxwin1.inl Line:21" the line causing error: myWnd.CreateEx(0, AfxRegisterWndClass(0), _T("My Window"), WS_OVERLAPPED, 0, 0, 0, 0, NULL, NULL) [myWnd derives CWnd class]

When the C++ application is run as exe, it has no problem no exception.

How to avoid this error?