Is there any possibility to programatically close Silverlight application on Windows Phone 7?
Short answer for Silverlight is No.
You should not provide a way to close the applicaiton. Closing the applicaiton should be the users choice and implemented by using the back button the appropriate number of times. This is also a marketplace requirement.
That said, a silverlight application will close if there is an unhandled exception. I have seen a few people try and create programmatic closing by throwing a custom error which is explicitly ignored in error handling. This can work but there is still the marketplace issue.
XNA applications can explictly call Exit()
.
If you write an XNA Game, you will have access to an explicit Exit() method. If you are writing traditional Silverlight project, then NO, there is no way to programatically close your app. See also Peter Torr's Blog entry on Exiting Silverlight Apps in Windows Phone 7. There he also mentions the option of throwing an unhandled exception, which IMO is a terrible programing style.
An option you may try, is using the WP7 Navigation Service to programatically navigate back out of the application. Not sure if that would work though. Why do you need to Exit?
Some good info here already. Adding to this..
The platform is fully capable of managing closure of apps. The more apps don't provide an exit, the quicker users will become accustomed to not thinking about app house keeping, and let the platform manage it.
The user will just navigate their device using start, back, etc.
If the user wants out of the current app to go do something else quickly - easy - they just hit start.
.Exit(), whilst available for xna, really isn't required anymore either. There was a cert requirement during CTP that games had to provide an exit button. This is now gone.
Non game apps never had the need to implement this.
The more this topic's discussed (and it really has been given a good run around the block), the more the indicators to me suggest there is no need to code an exit.