need to detect when new instance start

i need to detect when a new instance of my APP have been started .like the Windows Media Player when it is running and if we double click on a new song (test.mp3) media player can detect it and can play it with out running new instance ?
Thax for help me . :wave:

...I would hazard a guess that you might want to look at the App.Previnstance to see if your app has already been started elsewhere and then take whatever action you deem appropriate (hope this is on-topic!)