private void DeleteFastKeyOnClick(object sender, RoutedEventArgs e)
{
List <Item> items = (_isFirstFocused ? FirstPanel : SecondPanel).Items.Cast <Item>()
.Where(item => item.IsChecked).ToList();
OperationWindow operationWindow = new OperationWindow("Deleting");
operationWindow.OnFinish += (o, s) =>
{
UpdatePanels();
operationWindow.Close();
};
operationWindow.Show();
operationWindow.Delete(items);
UpdatePanels();
}
