Custom Renderers

One of the paramount features of the Xamarin.Forms toolkit is the layer of abstraction it provides over user interface implementation. With a single API, Xamarin.Forms allows you to use native user interface controls and functionality. For example, the Entry class at runtime will display a UITextField view on iOS, an EditText widget on Android, and a TextBox control on Windows. The toolkit does this by using a concept called Renderers. The renderers correspond with the visual elements—controls, pages, and layouts—within the API. So, for example, there is an EntryRenderer that is responsible for rendering instances of the Entry class down to the platform-specific versions of that control.

The beauty of this renderer concept is that you can subclass the various renderer classes to override how a specific element is translated at runtime. So, for example, if you wanted all textboxes in your app (that is, every time you display an Entry element) to be completely borderless, you...