private void DeleteButton_Click(object sender, RoutedEventArgs e)
        {
            Button button = sender as System.Windows.Controls.Button;
            Prefix user   = button.DataContext as Prefix;

            if (MessageBox.Show("Are you sure you want to delete " + user.Pre + " ?", "Confirmation", MessageBoxButton.YesNo) == MessageBoxResult.Yes)
            {
                user.Delete(user.Id.ToString());
                Refresh();
            }
            else
            {
                return;
            }
        }