Xamarin.Forms versus traditional Xamarin

While this book is about Xamarin.Forms, we will highlight the difference between using traditional Xamarin and Xamarin.Forms. Traditional Xamarin is used when developing applications that use iOS and Android SDK without any means of abstraction. For example, we can create an iOS app that defines its user interface in a storyboard or in the code directly. This code will not be reusable for other platforms, such as Android. Applications built using this approach can still share non-platform-specific code by simply referencing a .NET standard library. This relationship is shown in the following diagram:

Xamarin.Forms, on the other hand, is an abstraction of the GUI, which allows us to define user interfaces in a platform-agnostic way. It still builds on top of Xamarin.iOS, Xamarin.Android, and all other supported platforms. The Xamarin.Forms application can be created as a .NET standard library or as a shared code project, where the source files are linked as copies and built within the same project as the platform you are currently building for. This relationship is shown in the following diagram:

Having said that, Xamarin.Forms cannot exist without traditional Xamarin, since it's bootstrapped through an application for each platform. This gives you the ability to extend Xamarin.Forms on each platform using custom renderers and platform-specific code that can be exposed to your shared code base through interfaces. We'll look at these concepts in detail later in this chapter.