How can I automatically run some code when a WPF form is closed?
See Question&Answers more detail:osHow can I automatically run some code when a WPF form is closed?
See Question&Answers more detail:osJust attach an event handler to Window.Closed for your form.
It's also possible to do this in a more MVVM-friendly approach by creating a custom ICommand, and having it fire based off the event. Here is a blog post describing this approach.
Once you've done that, you can have a command on your ViewModel that will fire when the form closes.