"Prism is a fully open source version of the Prism guidance originally produced by Microsoft Patterns & Practices.  Prism provides an implementation of a collection of design patterns that are helpful in writing well structured and maintainable XAML applications, including MVVM, dependency injection, commanding, event aggregation, and more. Prism's core functionality is a shared code base in a Portable Class Library targeting these platforms; WPF, and Xamarin Forms. Features that need to be platform specific are implemented in the respective libraries for the target platform."