XamariniOS

XamariniOS, officially known as Xamarin.iOS, is a platform within the Xamarin framework that enables the development of native iOS applications using C# and the .NET runtime. It provides bindings to the iOS SDK, exposing APIs from UIKit, Foundation, CoreAnimation and other Apple frameworks to C# developers. Applications built with Xamarin.iOS run as native iOS binaries and can share business logic and data access code with other Xamarin platforms through shared projects or portable libraries, and can leverage Xamarin.Forms for cross-platform user interfaces where appropriate.

Development and build: building iOS apps requires a Mac with Xcode. Developers can use Visual Studio on Windows connected to a Mac build host, or operate on macOS with Visual Studio for Mac. A Xamarin.iOS project uses C# for application logic and can use Interface Builder or Xamarin.Forms for UI. iOS apps are ahead-of-time compiled and linked to the iOS SDK, producing a native app bundle that can be deployed to devices or submitted to the App Store.

History and ecosystem: Xamarin originated as MonoTouch and was later renamed Xamarin.iOS. Microsoft acquired Xamarin in 2016, and the tooling has been distributed as part of Visual Studio and the broader .NET ecosystem. Xamarin tools remain in use alongside Xamarin.Android and the evolving .NET MAUI framework, which aims to unify cross-platform UI development under .NET.

Limitations: development relies on Apple’s toolchain and a Mac build host; keeping up with iOS API updates may require tooling updates and new bindings. For iOS, AOT compilation is used to produce native binaries, and platform-specific behavior may require conditional code or bindings.