private void NavigationHelper_SaveState(object sender, SaveStateEventArgs e)

         {

             // TODO: 在此处保存页面的唯一状态。

             ApplicationDataContainer localsetting = Windows.Storage.ApplicationData.Current.LocalSettings;

             if ((String)localsetting.Values["AppCourt"] == "")

             {

                 localsetting.Values["AppCourt"] = "";

                 showMessageBox();

             }

             else if (localsetting.Values.ContainsKey("AppCourt"))

             {

                 localsetting.Values["AppCourt"] =(int.Parse((String)localsetting.Values["AppCourt"])+).ToString();

             }

             else

             {

                 localsetting.Values["AppCourt"] = "";

             }

         }

         async void  showMessageBox()

         {

             MessageDialog messagedialog = new MessageDialog("给个好评鼓励开发=_=");

             messagedialog.Commands.Add(new UICommand("好评",new UICommandInvokedHandler(this.CommandRateInvokedHandler)));

             messagedialog.Commands.Add(new UICommand("取消"));

             await messagedialog.ShowAsync();

         }