Invoke with timeout

Answer 1

Move the cross-process DCOM call to another thread. You are obviously hanging the UI thread, which is completely unacceptable. Fix that and your phantom problem (the OP) goes away too.

Answer 2

This is a common threading problem when it comes to running something on the GUI thread and this symptom affects all breeds of developers.

If you were to create a separate thread where you display the actual progress dialog and another thread to perform the DCOM call, it would simply entail moving the ManuaResetEvent synchronization between the two threads. This has the benefit of not locking the GUI thread since the separate thread that creates the progress form will have its own message queue created, and the second thread used to run the DCOM call does not have to lock any GUI thread.

It does require some careful sycnhronizing but once done, it's beautiful to see in action:

private ManualResetEvent _event = new ManualResetEvent(false);
...

private void StartTheComProgressCall()
{
    _event.Reset();

    ThreadPool.QueueUserWorkItem(StartProgressDialog);
    ThreadPool.QueueUserWorkItem(StartDCOMCall);

    // there's various possibilities to perform here, we could ideally 1) wait on the
    // event to complete, 2) run a callback delegate once everything is done
    // 3) fire an event once completed
}

private void StartProgressDialog(object state)
{
    ProgressDialog dialog = new ProgressDialog();
    dialog.Show();

    while(!_event.WaitOne(0))
        Application.DoEvents();

    dialog.Close();
}

private void StartDCOMCall()
{
    ...
   <perform your DCOM routines here>

    // once the call is done, remember to trigger that it's complete
    // so that blocking threads can continue to do what they need to do
    _event.Set();
}

Notes Some might argue against using the Application.DoEvents() method, but consider that DoEvents forces any pending Windows messages on the current calling thread's message queue to be processed and since the call is made in a different thread (the one that created the progress dialog) and not the GUI thread, there should be no more or ethical "code smell" issues with using it. We should use whatever tools or technique help us get the job done.