private void CreateUpdateButtonClicked(object sender, RoutedEventArgs e)
        {
            AddEditTodoDialog dlg = new AddEditTodoDialog(null);

            dlg.Owner = this;
            dlg.ShowDialog();
        }
 private void lstTodos_MouseDoubleClick(object sender, MouseButtonEventArgs e)
 {
     if (lstTodos.Items.Count != 0 && lstTodos.SelectedIndex != -1)
     {
         Todo todo             = (Todo)lstTodos.SelectedItem;
         AddEditTodoDialog dlg = new AddEditTodoDialog(todo);
         dlg.Owner = this;
         dlg.ShowDialog();
     }
 }