How to create a timer running in the background without blocking the UI thread with Xamarin?

If you need to do something at 1 second intervals, you might be able to use a timer for that. I have used code like this in Xamarin.Android myself:

   private void CountDown ()
    {

        System.Timers.Timer timer = new System.Timers.Timer();
        timer.Interval = 1000; 
        timer.Elapsed += OnTimedEvent;
        timer.Enabled = true;


    }

    private void OnTimedEvent(object sender, System.Timers.ElapsedEventArgs e)
    {

    }

OnTimedEvent will then fire every second and you can do your call in an async Task.