private async void TextBox_Loaded(object sender, RoutedEventArgs e)
{
StackPanel panel = sender as StackPanel;
ProgressBar progressBar = panel.Children[0] as ProgressBar;
AutoCompleteBox box = panel.Children[1] as AutoCompleteBox;
box.Visibility = Visibility.Collapsed;
await LoadItemsSourceTo(box, IsSource);
box.Visibility = Visibility.Visible;
progressBar.Visibility = Visibility.Collapsed;
box.Focus(FocusState.Pointer);
}
public static async Task LoadItemsSourceTo(AutoCompleteBox box, bool isSource)
{
box.PriorityComparer = new StopModelComparer();
box.ItemsSource = await boxItemSourceTask;
box.DefaultItems = isSource ? await defaultItemSourceSourcesTask : await defaultItemSourceTargetsTask;
}