问如果在不使用MessageDialog的情况下加载页面时隐藏几个控件，应用程序就会崩溃

EN

protected  override void OnNavigatedTo(NavigationEventArgs e)
    {

         .....
        // MUST ENABLE THE LOCATION CAPABILITY!!!
          var locator = new Geolocator();
          locator.DesiredAccuracyInMeters = 50;
          locator.ReportInterval = (uint)TimeSpan.FromSeconds(15).TotalMilliseconds;
          setloc(locator);
          this.navigationHelper.OnNavigatedTo(e);

    }

    public async void setloc(Geolocator locator)
    {
        if (locator.LocationStatus != PositionStatus.Disabled && (bool)Windows.Storage.ApplicationData.Current.RoamingSettings.Values["location"]==true)
        {
            var position = await locator.GetGeopositionAsync();
            await MyMap.TrySetViewAsync(position.Coordinate.Point, 16D);
            ....
            return;
        }
        else if (locator.LocationStatus == PositionStatus.Disabled && (bool)Windows.Storage.ApplicationData.Current.RoamingSettings.Values["location"] == true)
        {

            MessageDialog msgbox = new MessageDialog("Location Services are turned off. Please turn them on to save Location while saving a Tip", "Location Unavailable");
            await msgbox.ShowAsync();
            savebutton.Visibility = Visibility.Collapsed;
            myMapBlock.Visibility = Visibility.Collapsed;
            return;

        }
       ***// MessageDialog msgbox1 = new MessageDialog("Location Services are turned off. Please turn them on to save Location while saving a Tip", "Location Unavailable");
       // await msgbox1.ShowAsync();***

       savebutton.Visibility = Visibility.Collapsed;
       myMapBlock.Visibility = Visibility.Collapsed;

    }