Say my app has already up and running. If I hit Home key and click on the app's tile, I see that Application_Launching and "public MainPage()" is calling again. It looks like the app is restarted and it is actually doing that. Is this expected? If I do the same to Facebook app, it doesn't show the splash screen. How do they do that? I hope there is a way to know that user is launching from tile so that I can keep my music playing without being interrupted. Thanks!
I think you might be looking for "Fast app resume". You can find more information about it here.