How to terminate a Xamarin application?

If you are using Xamarin.Forms create a Dependency Service.

Interface

public interface ICloseApplication
{
    void closeApplication();
}

Android : Using FinishAffinity() won’t restart your activity. It will simply close the application.

public class CloseApplication : ICloseApplication
{
    public void closeApplication()
    {
        var activity = (Activity)Forms.Context;
        activity.FinishAffinity();
    }
}

IOS : As already suggested above.

public class CloseApplication : ICloseApplication
{
    public void closeApplication()
    {
        Thread.CurrentThread.Abort();
    }
}

UWP

public class CloseApplication : ICloseApplication
{
    public void closeApplication()
    {
        Application.Current.Exit();
    }
}

Usage in Xamarin Forms

var closer = DependencyService.Get<ICloseApplication>();
    closer?.closeApplication();