While designing the Web screen, you created the button which should allow the user to rate the game. You can easily implement this functionality with the MarketplaceReviewTask class, which is another launcher used in the exemplary game. You need to modify the Rate method of the WebViewModel class, as shown in the following code snippet:

private void Rate()
{
  MarketplaceReviewTask task = new MarketplaceReviewTask();
  task.Show();
}

Here, you create a new instance of the MarketplaceReviewTask class (from the Microsoft.Phone.Tasks namespace) and call the Show method. When this part of code is executed, the review page is opened, where the user can rate and review the current application.