private void DeleteFolder_Click(object sender, RoutedEventArgs e) { if (FolderListbox.SelectedItems != null) { Debug.WriteLine("SelectedItems is NOT null!"); var selectedFiles = FolderListbox.SelectedItems.Cast <string>().ToList(); foreach (var item in selectedFiles) { //printCollection(MyFolders); MyFolders.Remove(item); //Debug.WriteLine(item); PrintCollection(MyFolders); } } else { Debug.WriteLine("SelectedItems is null!"); } }