How to exit a WPF app programmatically?

To exit your application you can call

Application.Current.Shutdown();

As described in the documentation to the Application.Shutdown method you can also modify the shutdown behavior of your application by specifying a ShutdownMode:

Shutdown is implicitly called by Windows Presentation Foundation (WPF) in the following situations:

• When ShutdownMode is set to OnLastWindowClose.
• When the ShutdownMode is set to OnMainWindowClose.
• When a user ends a session and the SessionEnding event is either unhandled, or handled without cancellation.

Please also note that Application.Current.Shutdown(); may only be called from the thread that created the Application object, i.e. normally the main thread.