WPF(MVVM)主窗口关闭时 弹窗提示是否关闭

窗口设置为：

  Name="MianPage"
        WindowState="Maximized"
        Closing="Window_Closing"

在主窗口中：

 //关闭窗口事件
        //不知道与重写窗口关闭事件 OnClosed有什么区别
        private void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e)
        {
            //系统自动提示窗
            //MessageBoxResult result = MessageBox.Show("是否退出本系统？", "", MessageBoxButton.YesNo);
            //if (result == MessageBoxResult.No)
            //{
            //    e.Cancel = true;
            //}

            //自定义提示窗
            //取消窗口关闭 
            e.Cancel = true;
            //跳转到退出窗口
            LogDown logdown = new LogDown();
            //在父窗口中间显示，
            logdown.WindowStartupLocation = WindowStartupLocation.CenterOwner;
            logdown.Owner = this;
            logdown.Topmost = true;
            logdown.ShowDialog();
        }

自定义提示窗口：

public partial class LogDown : Window
    {
        public LogDown()
        {
            InitializeComponent();
            /*窗口固定在屏中*/
            WindowStartupLocation = WindowStartupLocation.CenterScreen;
        }

        //退出系统按钮
        private void Button_Click(object sender, RoutedEventArgs e)
        {
            // 强制退出，即使有其他的线程没有结束
            Environment.Exit(0);
            // 关闭当前程序，如果有其他线程没有结束，不会关闭
            //Application.Current.Shutdown();

        }
        //热键绑定
        private void CommandBinding_CanExecute1(object sender, CanExecuteRoutedEventArgs e)
        {
            e.CanExecute = true;
        }

        private void CommandBinding_Executed1(object sender, ExecutedRoutedEventArgs e)
        {
            Button_Click(this, null);
        }

        //不退出系统按钮
        private void Button_Click_1(object sender, RoutedEventArgs e)
        {
            this.Close();// 关闭当前窗口，可以在OnClosing和 OnClosed中捕获消息，在OnClosing的时候，可以取消关闭窗口。
        }

        /// 

        /// 热键绑定
        /// 
        /// 
        /// 
        private void CommandBinding_CanExecute2(object sender, CanExecuteRoutedEventArgs e)
        {
            e.CanExecute = true;
        }

        private void CommandBinding_Executed2(object sender, ExecutedRoutedEventArgs e)
        {
            Button_Click_1(this, null);
        }
       

    }