private void NavigationHelper_SaveState(object sender, SaveStateEventArgs e)
        {
            ViewModel.OnStop();

            GeofenceMonitor.Current.GeofenceStateChanged -= OnGeofenceStateChanged;

            locator.PositionChanged -= LocatorPositionChanged;

            ViewModel.AlarmScreenRequired -= ViewModel_AlarmScreenRequired;
            ViewModel.AddScreenRequired -= ViewModel_AddScreenRequired;
            ViewModel.AlarmsChanged -= ViewModel_AlarmsChanged;
            ViewModel.MapZoomChanged -= ViewModel_MapZoomChanged;
        }
 void NavigationHelper_SaveState(object sender, SaveStateEventArgs e)
 {
     ViewModel.Saved -= OnSaved;
     ViewModel.PropertyChanged -= ViewModel_PropertyChanged;
 }
		private void NavigationHelper_SaveState(object sender, SaveStateEventArgs e)
		{
		}