Here you can find the ready made code for some xamarin basic approaches.
Xamarin.Forms is a cross-platform natively backed UI toolkit abstraction that allows developers to easily create user interfaces that can be shared across Android, iOS, Windows, and the Universal Windows Platform. The user interfaces are rendered using the native controls of the target platform, allowing Xamarin.Forms applications to retain the appropriate look and feel for each platform. This article provides an introduction to Xamarin.Forms and how to get started writing applications with it.
Xamarin.Android Xamarin.Android exposes the complete Android SDK for .NET developers. Build fully native Android apps using C# or F# in Visual Studio.
Xamarin.iOS Xamarin.iOS exposes the complete iOS SDK for .NET developers. Build fully native iOS apps using C# or F# in Visual Studio.