wpf metro 点右上角关闭询问是否关闭

MainWindow.xaml中，添加Closing="MetroWindow_Closing"

在窗体的属性为Closing事件绑定方法

MainWindow.xaml.cs中

    　　using System.Threading;


　　　　 #region 窗体关闭
        /// <summary>
        /// 窗体关闭
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void MetroWindow_Closing(object sender, System.ComponentModel.CancelEventArgs e)
        {
            e.Cancel = true;
            CancellationToken token;
            TaskScheduler uiSched = TaskScheduler.FromCurrentSynchronizationContext();
            Task.Factory.StartNew(DialogsBeforeExit, token, TaskCreationOptions.None, uiSched);

        }



        /// <summary>
        /// 关闭窗体之前的提示对话框
        /// </summary>
        private async void DialogsBeforeExit()
        {
            MessageDialogResult result = await this.ShowMessageAsync(this.Title, "您真的要离开吗?", MessageDialogStyle.AffirmativeAndNegative);
            if (result == MessageDialogResult.Negative)
            {
                return;
            }
            else//确认退出
            {

                System.Environment.Exit(System.Environment.ExitCode);//关闭程序
            }
        }
        #endregion