I have read in requirements that when user presses the back button, application must exit. (5.4.2): "Pressing the Back button from the first screen of an application must exit the application".
So, i have read in many sites that exitting in silverlight is not available, but i think that they mean, that application should only deactivate (for example, it is deactivated when we press button with "windows flag"). I have a main menu in my application. If i navigate on another pages and return to main menu, pressing "back button" doesn't deactivate application because previous pages are another pages in application. So, maybe I need to clean "navigation history" ? But it is not possible, i have readed it somewhere... so, what to do in this case?