Xamarin

 Xamarin

Xamarin is a cross-platform development framework created by Microsoft that allows developers to build native mobile applications for iOS, Android, and Windows using a single shared codebase in C#. Developers can use various development tools such as Visual Studio and Xamarin Studio to develop mobile applications. 

Here's an example of code in C# to create a button in Xamarin.Forms:

<Button Text="Click me"

        Clicked="OnButtonClicked" />