How can I tell if a process has a graphical interface?

Question

I\'m using automation to test an application, but sometimes I want to start the application via a batch file. When I run \"process.WaitForInputIdle(100)\" I get an error:

Answer 1

As well as a MainWindowHandle check, one can enumerate the process threads and check if any of them reference a visible window via P/Invokes. This seems to do a good job catching any windows that the first check misses.

private Boolean isProcessWindowed(Process externalProcess)
{
    if (externalProcess.MainWindowHandle != IntPtr.Zero)
    {
        return true;
    }

    foreach (ProcessThread threadInfo in externalProcess.Threads)
    {
        IntPtr[] windows = GetWindowHandlesForThread(threadInfo.Id);

        if (windows != null)
        {
            foreach (IntPtr handle in windows)
            {
                if (IsWindowVisible(handle))
                {
                    return true;
                }
            }
        }
    }

    return false;
}

private IntPtr[] GetWindowHandlesForThread(int threadHandle)
{
    results.Clear();
    EnumWindows(WindowEnum, threadHandle);

    return results.ToArray();
}

private delegate int EnumWindowsProc(IntPtr hwnd, int lParam);

private List results = new List();

private int WindowEnum(IntPtr hWnd, int lParam)
{
    int processID = 0;
    int threadID = GetWindowThreadProcessId(hWnd, out processID);
    if (threadID == lParam)
    {
        results.Add(hWnd);
    }

    return 1;
}

[DllImport("user32.Dll")]
private static extern int EnumWindows(EnumWindowsProc x, int y);
[DllImport("user32.dll")]
public static extern int GetWindowThreadProcessId(IntPtr handle, out int processId);
[DllImport("user32.dll")]
static extern bool IsWindowVisible(IntPtr hWnd);