Portable Class Libraries (PCL) support the cross-platform development of .NET Framework applications. With Portable Class Libraries, you can write portable assemblies that share code with Windows 8, Windows Phone, Xbox 360 and other .NET applications. If you choose not to use them, then you must target a single application type and rework the class library for other application types as needed. PCLs save this work by allowing you to build assemblies that are shared across different platforms. In this article, we are going to use the MVVM (Model-View-View-Model) pattern with Portable Class Libraries that target Windows 8 apps and more! Let’s get started.