private void OnKeyDown(object sender, KeyEventArgs e)
 {
     if (e.Key == Key.A && Keyboard.IsKeyDown(Key.LeftCtrl))
     {
         DownloadItemsListBox.SelectAll();
     }
 }
 private void SelectAllButtonOnClick(object sender, RoutedEventArgs e)
 {
     DownloadItemsListBox.SelectAll();
     ContextMenuPopup.IsOpen = false;
 }
 private void SelectAllButtonOnClick(object sender, RoutedEventArgs e)
 {
     DownloadItemsListBox.SelectAll();
 }