Disable WPF buttons during longer running process, the MVVM way

Question

I have a WPF/MVVM app, which consists of one window with a few buttons.
Each of the buttons triggers a call to an external device (an USB missile launcher), which takes

Answer 1

Because you run CallExternalDevice() on the main thread, the main thread won't have time to update any UI until that job is done, which is why the buttons remain enabled. You could start your long-running operation in a separate thread, and you should see that the buttons are disabled as expected:

private void CallExternalDevice(object obj)
{
    this.disableGui = true;

    ThreadStart work = () =>
    {
        // simulate call to external device (USB missile launcher),
        // which takes a few seconds and pauses the app
        Thread.Sleep(3000);

        this.disableGui = false;
        Application.Current.Dispatcher.BeginInvoke(new Action(() => CommandManager.InvalidateRequerySuggested()));
    };
    new Thread(work).Start();
}