private void UnarchiveOnClick(object sender, RoutedEventArgs e)
        {
            OperationWindow operationWindow = new OperationWindow("Unarchiving");

            operationWindow.OnFinish += (o, args) =>
            {
                operationWindow.Close();
                UpdatePanels();
            };
            List <Item> items = (_isFirstFocused ? FirstPanel : SecondPanel).Items.Cast <Item>()
                                .Where(item => item.IsChecked).ToList();

            if (items.Count < 1)
            {
                return;
            }
            operationWindow.Show();
            operationWindow.Unarchive(items[0]);
            UpdatePanels();
        }