Invalid Menu Handle in DLL project

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C++

Hello

I have been trying to create a DLL in C++ using Visual Studio 2012. The aim is to convert the BasicPlayback sample which uses the Microsoft Media Foundation to play a video file into a DLL that does the same thing.

The sample can be found in MFSamples.zip at :
http://archive.msdn.microsoft.com/mediafoundation

The BasicPlay sample compiles and runs showing a window with a File Menu. However, when I convert it to a dll and call the relevant function (see later), the window displays without a menu. I use GetLastError after the CreateWindow function and I get "Invalid Menu Handle". The thing is I am not sure what is going wrong.

To create the DLL, I create a empty Win32 DLL project. I copy over the .H, .CPP, .RC files from BasicPlayback folder and add them to the Header Files, Resource Files and Source files in Solution explorer. I then copy the Additional Dependencies using the VS Menu(Project, Properties, Linker, Input) and overwrite the Additional Dependencies of the DLL project.

I change the WinMain function from this:

int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PWSTR pCmdLine, int nCmdShow)
{
    MSG msg;

    ZeroMemory(&msg, sizeof(msg));

    // Perform application initialization.
    if (!InitInstance(hInstance, nCmdShow))
    {
        NotifyError(NULL, L"Could not initialize the application.",
            HRESULT_FROM_WIN32(GetLastError()));
        return FALSE;
    }

    // Main message loop.
    while (GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    // Clean up.
    if (g_pPlayer)
    {
        g_pPlayer->Shutdown();
        g_pPlayer->Release();
    }
    return 0;
}

To to this (e.g. I change the function name) :

<pre lang="cs">extern "C"
{
    // int PlayMovie(HINSTANCE hInstance)
    __declspec(dllexport) int PlayMovie(HINSTANCE hInstance)
    {
        MSG msg;

        ZeroMemory(&msg, sizeof(msg));

        // Perform application initialization.
        if (!InitInstance(hInstance, 0))
        {
            NotifyError(NULL, L"Could not initialize the application.",
                HRESULT_FROM_WIN32(GetLastError()));
            return FALSE;
        }

        // Main message loop.
        while (GetMessage(&msg, NULL, 0, 0))
        {
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }

        // Clean up.
        if (g_pPlayer)
        {
            g_pPlayer->Shutdown();
            g_pPlayer->Release();
        }
        return 0;
    }
}

I then call the PlayMovie function from within a c# program by including the following:

[DllImport(@"BasicDll.dll", EntryPoint="PlayMovie", ExactSpelling=false,CallingConvention=CallingConvention.Cdecl)]
public static extern int PlayMovie(IntPtr hInstance);

I then call the PlayMovie function as follows:

IntPtr windowHandle = new WindowInteropHelper(this).Handle;
PlayMovie(windowHandle);

The dll project compiles without error or warning. When I call the PlayMovie function from c#, the window opens as expected. However the Menu is missing.

Investigating with GetLastError finds the problem to be here (Maybe??? but I'm not sure) :

BOOL InitInstance(HINSTANCE hInst, int nCmdShow)
{
	HWND hwnd;
	WNDCLASSEX wcex;

	g_hInstance = hInst; // Store the instance handle.

	// Register the window class.
	ZeroMemory(&wcex, sizeof(WNDCLASSEX));
	wcex.cbSize         = sizeof(WNDCLASSEX);
	wcex.style          = CS_HREDRAW | CS_VREDRAW;
	wcex.lpfnWndProc    = WndProc;
	wcex.hInstance      = hInst;
	wcex.hbrBackground  = (HBRUSH)(COLOR_WINDOW+1);
	wcex.lpszMenuName   = MAKEINTRESOURCE(IDC_MFPLAYBACK);
	wcex.lpszClassName  = szWindowClass;

	if (RegisterClassEx(&wcex) == 0)
	{
		return FALSE;
	}

	// Create the application window.
	hwnd = CreateWindow(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW,
		CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, NULL, NULL, hInst, NULL);

	if (hwnd == 0)
	{
		return FALSE;
	}

	ShowWindow(hwnd, SW_SHOW);
	UpdateWindow(hwnd);

	return TRUE;
}

Using GetLastError after CreateWindow Gives 1401 Invalid Menu Handle.

Now, since the project work as an exe and given the steps I used to create the dll, I am at a loss to know what has gone wrong. However, I am not experienced with DLLs and Windows programming so it could easily be something silly. I was hoping someone could through me a few clues as to what I've done wrong....I have strggle to find the solution on Google...

Many thanks....