I think the problem with this one has to do with the window count as well as the MainWindow property. As you noticed with the first example posted, showing a dialog and closing it causes the app to shut down as the MainWindow property is nulled. The same is happening here, and if you do happen to change the ShutdownMode to OnLastWindowClose, you get essentially the same behavior, because the first window (the dialog) is opened, and then the last window (the dialog) is closed (shutting down the app), before the next window is instantiated. I haven’t tested, but would be willing to bet that if you set the ShutdownMode to Explicit, you would not get this (not neccessarily recommended, just saying…)

All that said, many thanks for the post. As a relative newbie to any programming other than VBA, this got me really digging around in WPF application lifetime management. If you like, I can post the MSDN links where I found this info (along with many other related and quite helpful topics).

Cheers and thanks again,
j.

Just remember to *remove* the StartupUri in Application element at app.xaml.

I was in a hurry and missed that. (Looking only the source code)

public class MyApp : Application
{
protected override void OnStartUp(object sender, StartUpEventArgs e)
{
MainWindow window = new MainWindow();
MyConfigDialog dialog = new MyConfigDialog();
dialog.ShowDialog();

// Problem: The application doesn’t close when mainwindow is closed.
// window.Show(); // If you uncomment this it shows *two* main windowes. But same problem, application never closes.
}
}