Updating the App.xaml class to use the navigation service

Now that we have successfully updated each of our ViewModels and ContentPages to take advantage of our NavigationService so that our ViewModels will be able to navigate to each ViewModel and ContentPage within the navigation stack, the next step is to make some additional changes within our OnStart method. We do this in order to declare a NavService property that will be used to navigate between each of our ViewModels, as well as create an instance of our navigation service class.

Finally, we will see how to register each of our ViewModels and ContentPages on our navigation stack and check to see what Target OS Platform we are running on so that we can call the appropriate NavigationPage.

Let's take a look at how we can achieve this by following these steps:

1. Open the App.xaml.cs file, ensuring that it is displayed within the code editor, and enter the following highlighted code sections:

     //
     //  App.xaml.cs
     //  Main class...