wp7 tombstone墓碑机制

      主要用到PhoneApplicationService类 ，也可以用独立存储保存数据吧。可能这个类里面微软做一些优化。

      用法很简单，重写页面方法，在用户离开之前，将数据保存起来；在用户再一次进来时，将数据显示出来。很简单吧

      //进入页面
        protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
        {
             base.OnNavigatedTo(e);
             PhoneApplicationService phoneService = PhoneApplicationService.Current;
             IDictionary<string, object> dics = phoneService.State; //字典
             if (dics.ContainsKey("day02"))
             {
                 textBlock01.Text = dics["day02"].ToString();
             }
        }

        //退出页面
        protected override void OnNavigatedFrom(System.Windows.Navigation.NavigationEventArgs e)
        {
              base.OnNavigatedFrom(e);
              PhoneApplicationService phoneService = PhoneApplicationService.Current;
              IDictionary<string, object> dics = phoneService.State;
              dics["day02"] = textBlock01.Text;
        }