关闭窗体前触发事件

有时有关闭窗体前需要触发事件，如退出前自动备份、确认退出等

在窗体标记里添加Closing事件： Closing="Window_Closing"

   private void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e)
        {
            MessageBoxResult key = MessageBox.Show(
                "Are you sure you want to quit",
                "Confirm",
                MessageBoxButton.YesNo,
                MessageBoxImage.Question,
                MessageBoxResult.No);
            e.Cancel = (key == MessageBoxResult.No);
        }