Defining a UI using XAML

The most common way to declare our UI in Xamarin.Forms is by defining it in a XAML document. It is also possible to create the GUI in C#, since XAML is really only a markup language for instantiating objects. We could, in theory, use XAML to create any type of object, as long as it has a parameterless constructor. A XAML document is an Extensible Markup Language (XML) document with a specific schema.