Thanks guys for response. I tried depends and added the necessary dll for that and GetLastError too. And according to that The operation was successful.

That depends on the interface of the DLL. If COM-dll or C-dll that static link to the CRT then no problem. If exporting C++ interfaces that makes use of the STL or uses shared heap, then the DLL must be compiled using the same version of Visual Studio.

See here - it may help.

Thats exactly your problem. The easiest way to solve this problem is, that you only call gui functions from within your thread that created the gui. In general calling gui functions from within a thread that didn't created the gui is not a good practice and often causes such problems. The are ways to do this, but its too long ago, that I developed C++. Maybe somebody can you explain how to do such calls. Greetings Covean