This document discusses using Xamarin to develop iOS apps using C#. Xamarin allows developers to write C# code and share code across iOS, Android, and other platforms. It works by using Mono, which implements .NET on mobile, and bindings that expose the iOS SDK in C#. The compiler produces native ARM binaries. Development can be done in Xamarin Studio on Mac or Visual Studio on Windows via a build host. Code signing and deployment require Xcode and the Apple developer program. Components and code can be shared between apps and with other developers.