C#/XAML on the front-end could mean that .Net/WPF is rendering the XAML and wiring up the C#. The C# might do little more than handle events triggered by the user interface and update the user interface in response to events triggered by the back end.

As the potential capabilities in front-end web development increase, the differences between web development and "desktop" software development are reduced, because web developers find themselves facing more and more of the same questions software developers have always faced when dealing with distributed software architectures at scale.