检测外部进程是否是交互式的并且是否有任何可见的 UI

Question

I cannot seem to find a way to determine whether a Process has a user interface eg a window, which is visible to the user?

• Environment.UserInteractive is not useful for external processes
• process.MainWindowHandle.= IntPtr.Zero appears to always return false in my tests?

I would like to differentiate between say Notepad and conhost

Answer 1

1. Find out the process ID from your Process instance.
2. Enumerate the top-level windows with EnumWindows .
3. Call GetWindowThreadProcessId and see if it matches the target PID.
4. Call IsWindowVisible and/or IsIconic to test if that window is visible to the user.

Answer 2

The MSDN article about System.Diagnostics.Process.MainWindowHandle states the following

If you have just started a process and want to use its main window handle, consider using the WaitForInputIdle method to allow the process to finish starting, ensuring that the main window handle has been created. Otherwise, an exception will be thrown.

What they are implying is that the Window might take several seconds to render after you've made the call for the MainWindowHandle , returning IntPtr.Zero even though you can clearly see a Window is shown.

See https://msdn.microsoft.com/en-us/library/system.diagnostics.process.mainwindowhandle(v=vs.110).aspx for reference

Answer 3

Following @David Heffernan, this is what I did:

HWND FindTopWindow(DWORD pid)
{
    std::pair<HWND, DWORD> params = { 0, pid };

    // Enumerate the windows using a lambda to process each window
    BOOL bResult = EnumWindows([](HWND hwnd, LPARAM lParam) -> BOOL
    {
        auto pParams = (std::pair<HWND, DWORD>*)(lParam);

        DWORD processId;
        if (GetWindowThreadProcessId(hwnd, &processId) && processId == pParams->second)
        {
            if (IsWindowVisible(hwnd)) {
                // Stop enumerating
                SetLastError(-1);
                pParams->first = hwnd;
                return FALSE;
            }

            return TRUE;
        }

        // Continue enumerating
        return TRUE;
    }, (LPARAM)&params);

    if (!bResult && GetLastError() == -1 && params.first)
    {
        return params.first;
    }

    return 0;
}