private async void ListSource_OnKeyDown(object sender, KeyRoutedEventArgs e)
 {
     if ((sender == null && e == null) || e.Key == VirtualKey.Enter)
     {
         e.Handled = true;
         TxtListSource.IsEnabled = false; //reset input
         TxtListSource.IsEnabled = true;
         FlyoutListSource.Hide();
         BottomCommandBar.IsOpen = false;
         await ViewModel.FetchData();
     }
 }
 private void ShowListSourceFlyout(object sender, RoutedEventArgs e)
 {
     FlyoutListSource.ShowAt(sender as FrameworkElement);
 }