Summary
Note
.NET MAUI is the next evolution of Xamarin and what we recommend you develop mobile and desktop apps with, and you can learn more about .NET MAUI in several training modules. This Xamarin training module will not be maintained going forward.
Modern applications typically connect to back-end services to provide social and cross-device experiences. It's rare to find applications that are isolated and have no connection to the internet.
In Xamarin.Forms, you can use HttpClient to consume REST web services and perform CRUD operations. Xamarin.Forms also has APIs that you can use to detect if you have an internet connection. This information is important because if you run code that uses the internet without a network connection, your application could stop responding. Finally, both Xamarin.iOS and Xamarin.Android have native networking stacks that we can take advantage of with HttpClient by using message handlers.