If you want to integrate the option for the user to rate and review within the app , you can use the LaunchUriAsync method to do it.
Below is a sample code snippet that demonstrates how to do it.
How to allow user to review apps within Windows Phone 8.1 Universal Apps ?
await Windows.System.Launcher.LaunchUriAsync(new Uri("ms-windows-store:reviewapp?appid="AbundantcodeAppID"));