Android background service closes when I close application. How i doing wrong?

I trying to make service, which leave running in background while I close the application. I used the example from: https://github.com/xamarin/recipes/blob/master/android/fundamentals/service/create_a_simple_service/SimpleService

and I removed StopService(new Intent(this, typeof (SimpleService))); from Activity1.cs , but the service stopping when I close Main activity. How I doing wrong? Please help me.