第一次加载程序：

This is App

This is Application_Launching

This is MainPage()

This is OnNavigatedTo

This is MainPage_Loaded()

返回键离开：

This is OnNavigatingFrom

This is OnNavigatedFrom

This is Application_Closing

This is ~MainPage()

Home键离开：

This is OnNavigatingFrom

This is OnNavigatedFrom

This is Application_Deactivated

Home键离开后启动：

This is Application_Activated

This is OnNavigatedTo

以上就是WP8程序开启离开的常用事件运行顺序，仅供像我一样的菜鸟学习；

扩展：上面顺序就可以很好解释下面（为什么NavigationContext在构造函数写的话会出现NullReference）：

发送页面发送字符串：NavigationService.Navigate(new  Uri("/Page.2xaml?msg=" + textBox1.Text,  UriKind.Relative));

接受页面接受字符串：protected override void OnNavigatedTo( System.Windows.Navigation.NavigationEventArgs e) { 　　base.OnNavigatedTo(e); 　　string msg = string.Empty; 　　if (NavigationContext.QueryString.TryGetValue("msg", out msg)) 　　{　　　　textBlock1.Text = msg 　　} }