Closing OpenFileDialog/SaveFileDialog

Question

We have a requirement to close child form as part of auto logoff. We can close the child forms by iterating Application.OpenForms from the timer thread. We are not able to c

Answer 1

My answer is conceptually similar to Hans Passant's answer.

However, using GetCurrentThreadId() as the tid parameter to EnumThreadWindows did not work for me since I was calling it from another thread. If you're doing that, then either enumerate the process' thread IDs and try each one until you find the windows you need:

ProcessThreadCollection currentThreads = Process.GetCurrentProcess().Threads;
foreach (ProcessThread thread in currentThreads) {
    CloseAllDialogs(thread.Id);
}

Or save off the thread IDs that do the ShowDialog to open the CommonDialog:

threadId = GetCurrentThreadId();
threadIds.Add(threadId);
result = dialog.ShowDialog()
threadIds.Remove(threadId);

and then:

foreach (int threadId in threadIds) {
    CloseAllDialogs(threadId);
}

Where CloseAllDialogs looks like:

public void CloseAllDialogs(int threadId) {
    EnumThreadWndProc callback = new EnumThreadWndProc(checkIfHWNDPointsToWindowsDialog);
    EnumThreadWindows(threadId, callback, IntPtr.Zero);
    GC.KeepAlive(callback);
}

private bool checkIfHWNDPointsToWindowsDialog(IntPtr hWnd, IntPtr lp) {
    StringBuilder sb = new StringBuilder(260);
    GetClassName(hWnd, sb, sb.Capacity);
    if (sb.ToString() == "#32770") {
        SendMessage(hWnd, 0x0010, IntPtr.Zero, IntPtr.Zero);
    }
    return true;
}

private delegate bool EnumThreadWndProc(IntPtr hWnd, IntPtr lp);

[DllImport("user32.dll", SetLastError = true)]
private static extern bool EnumThreadWindows(int tid, EnumThreadWndProc callback, IntPtr lp);

[DllImport("kernel32.dll", SetLastError = true)]
private static extern int GetCurrentThreadId();

[DllImport("user32.dll", SetLastError = true)]
private static extern int GetClassName(IntPtr hWnd, StringBuilder buffer, int buflen);

[DllImport("user32.dll", SetLastError = true)]
private static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wp, IntPtr lp);