Page State in Windows Phone 7 applications - do I need to save it?

In the following blog post the author describes the need to store page state, e.g. the text within a TextBox control, in the Page State dictionary so that it is restored when navigating between pages:

http://www.wintellect.com/CS/blogs/jgarland/archive/2011/01/26/a-matter-of-state-part-1.aspx

However, I have created a very simple application that has one page with a Bu开发者_开发知识库tton and a TextBlock and a ListBox of items. The button navigates to a dummy page, via NavigationService.Navigate. Now, if I scroll the list and input some text into my TextBox, navigate to the dummy page, then hit the back-button, I can see that my text is still present in the TextBox and the scroll position was preserved.

My question is, (tombstoning aside) do I ever need to persist the state of UI controls when simply navigating between them? It would appear that the frameowkr does this for me (despite the blog post above!).

You should persist state if it makes sense in the context of your application and will be helpful to the user.

This almost certainly means when tombstoning but probably not when the application is closed via the back button and then restarted.

In your scenario, the scroll position and text will be lost on tombstoning so you probably want to save these details.
Saving state is only relevant in the context of tombstoning and launching new instances of an application so (a tiny number of exceptional cases aside—and it doesn't sound like you are one of them) it doesn't make sense to talk about saving state outside of this.