Read original post by David Britch at Dave's Tech Blog
Previously I extended the sample photo viewing app so that the user can covert a colour photo to greyscale, on the PhotoPage. This used MVVM and commands to bind the Command property of a Checkbox control to a DelegateCommand property on the PhotoPageViewModel. When the control’s command is invoked, the code in the view model is executed.
In this blog post I’ll further extend the app so that page state can be serialized during suspension, and de-serialized when the app reactivates. Specifically, theIsGreyscale property of the PhotoPageViewModel class will be serialized/de-serialized so that when the app reactivates following termination, the state of the Checkbox control will be identical to when the app was suspended. Prism for the Windows Runtime makes performing this task very straight forward.