notify user to play sound windows phone 8 and stop current music - audio

Question

In my Windows Phone 7 and 7.5 apps I used to prompt a message box when the app was launched if the user was already playing music, to notify the user to stop current music to play the sounds, or to exit the app, this was working, but when I coded from the beginning for Windows Phone 8, for some reason this code doesn't work, if you are playing a sound, instead to prompt the notification, the apps opens and close itself.
This is the code I was using:
private void Application_Launching(object sender, LaunchingEventArgs e)
{
FrameworkDispatcher.Update();
if (MediaPlayer.GameHasControl != true)
{
if (MessageBox.Show("This application requires play sounds and stop your currently playlist", "Information",
MessageBoxButton.OK) == MessageBoxResult.OK)
{
MediaPlayer.Stop();
FrameworkDispatcher.Update();
}
}
}
I'm pretty sure must be some change in the Api with the MediaPlayer? I couldn't find any information about that, someone knows how can I fix that?
Thanks!!!

Answer 1

As you guessed,there are some changes in APIs.
First thing I notice, calling MessageBox.Show(string) from the Application_Launching event causes an exception. You app is probably shutting down due to an unhandled exception.
From MSDN: "If you call Show(String) method from the app Activated and Launching event handlers an InvalidOperationException is thrown with the message Error Displaying MessageBox."
EDIT: The documentation on MSDN is unclear whether calling .Show(string, string, messageBoxButton) raises the same exception.
App platform compatibility for Windows Phone