As a simple workaround, you create such a list manually. For example, use an ID property of type int to determine the id of the item in the list. When the user clicks the previous/next Button, you search for the item with the previous/next id in the list, and display it in the ContentControl.
shanaolanxing - I'll transfer to the Windows Azure team, and will have limited time to participate in the Silverlight forum. Apologize if I don't answer your questions in time.