Follow these steps to update an existing Xamarin.iOS app to use the Unified API. Updating an existing app to use the Unified API requires changes to the project file itself as well as to the namespaces and APIs used in the application code. The Road to 64 Bits The new Unified APIs are required to support 64 bit device architectures from a Xamarin.iOS mobile application. As of February 1st, 2015 Ap