How to quit a wp7 app? [duplicate]

Possible Duplicate:

Windows Phone 7 close application

I have an app which needs quiting from the MainPage but just using NavigationService.GoBack() won't work when another screen has navigated to that main page as I don't want the ability to go back to that previous page.

Would I have to set a variable in App.xaml.cs called backToBeginning and all the onnavigatedto callbacks will GoBack() if that is set? or is that too messy?

WP7 does not support exiting of apps. Just let the user do it with the back button.

Currently, there is no way to achieve this. What you have described is really needed in the Music+Video hub, but due to inability to to it with the way navigation in WP7 is organized, even Microsoft had to sacrifice the functionality of a very important build-in application.