Windows Phone persistent instance of page through app life-time
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I am working on a simple Windows Phone app, which has basically those functionality:

 - Page 1, there is a button to get user's location, and navigate to page 2
 - Page 2, use the user location and map control to display a map and view center is user's location. There is a app bar button to navigate to Page 3.
 - Page 3, Show some nearby place list in this page, and once user select one of the places, it will go back to page 2 to Pin the place on Map Control.

So here is the question: <br>I want to keep page 2 data alive in this case so I dont have to re-initialize page 2 everytime I go back from page 3. It would be perfect I can keep an instance of page 2 somewhere, and use that everytime I want to come back from page 2. So far I know there are two approach, one is in Page2 xaml I can have something like:

    <Page
      x:class "Page2.keepPageAlive"
      ...

The other one is using [AddBackEntry][1]. But I am not sure which one is fit in my case, or is there any other good approach. 

Please share your idea, thank you.


  [1]: http://msdn.microsoft.com/en-us/library/system.windows.navigation.navigationservice.addbackentry.aspx