How do I GetModuleFileName() if I only have a window handle (hWnd)?

Been struggling with the same problem for an hour now, also got the first letter replaced by a ? by using GetModuleFileNameEx. Finaly came up with this solution using the System.Diagnostics.Process class.

[DllImport("user32.dll")]
public static extern IntPtr GetWindowThreadProcessId(IntPtr hWnd, IntPtr ProcessId);

void GetProcessPathFromWindowHandle(IntPtr hwnd)
{
   uint pid = 0;
   Win32.GetWindowThreadProcessId(hwnd, out pid);
   Process p = Process.GetProcessById((int)pid);
   return p.MainModule.FileName;
}

You can call GetWindowThreadProcessId and that will return you the process associated with the window.

From that, you can call OpenProcess to open the process and get the handle to the process.

If you are running on a windows 64 bit platform, you may need to use QueryFullProcessImageName instead. This returns a user style path, compared to GetProcessImageFileName which returns a system style path that would need to be converted using NtQuerySymbolicLinkObject or ZwQuerySymbolicLinkObject.

One mammoth example function - recommend breaking up into re usable bits.

typedef DWORD (__stdcall *PfnQueryFullProcessImageName)(HANDLE hProcess, DWORD dwFlags, LPTSTR lpImageFileName, PDWORD nSize);
typedef DWORD (__stdcall *PfnGetModuleFileNameEx)(HANDLE hProcess, HMODULE hModule, LPTSTR lpImageFileName, DWORD nSize);

std::wstring GetExeName( HWND hWnd ){
// Convert from Window to Process ID
DWORD dwProcessID = 0;
::GetWindowThreadProcessId(hWnd, &dwProcessID);

// Get a handle to the process from the Process ID
HANDLE hProcess = ::OpenProcess(PROCESS_QUERY_INFORMATION | PROCESS_VM_READ, FALSE, dwProcessID);

// Get the process name
if (NULL != hProcess) {
    TCHAR szEXEName[MAX_PATH*2] = {L'\0'};
    DWORD nExeName = sizeof(szEXEName)/sizeof(TCHAR);

    //  the QueryFullProcessImageNameW does not exist on W2K
    HINSTANCE hKernal32dll = LoadLibrary(L"kernel32.dll");
    PfnQueryFullProcessImageName pfnQueryFullProcessImageName = NULL;
    if(hKernal32dll != NULL) {
        pfnQueryFullProcessImageName = (PfnQueryFullProcessImageName)GetProcAddress(hKernal32dll, "QueryFullProcessImageNameW");
        if (pfnQueryFullProcessImageName != NULL) 
            pfnQueryFullProcessImageName(hProcess, 0, szEXEName, &nExeName);
        ::FreeLibrary(hKernal32dll);
    } 

    // The following was not working from 32 querying of 64 bit processes
    // Use as backup for when function above is not available 
    if( pfnQueryFullProcessImageName == NULL ){ 
        HINSTANCE hPsapidll = LoadLibrary(L"Psapi.dll");
        PfnGetModuleFileNameEx pfnGetModuleFileNameEx = (PfnGetModuleFileNameEx)GetProcAddress(hPsapidll, "GetModuleFileNameExW");
        if( pfnGetModuleFileNameEx != NULL )    
            pfnGetModuleFileNameEx(hProcess, NULL, szEXEName, sizeof(szEXEName)/sizeof(TCHAR));
        ::FreeLibrary(hPsapidll);
    }

    ::CloseHandle(hProcess);

    return( szEXEName );
} 
return std::wstring();
}