I’m working on a cross platform application. To re-use most of the code we are refactoring the existing components to use the Portal Libraries.
The Portable Class Library project in Visual Studio 2012 supports the cross-platform development of .NET Framework apps.
Use this project to write and build portable assemblies that work without modification on multiple platforms, such as Windows 7, Windows 8, Silverlight, Windows Phone, and Xbox 360. For example, you can create classes that contain shared business logic for desktop apps, Windows Store apps, and mobile apps, and you can then reference those classes from your apps.
The Portable Class Library project supports a subset of assemblies from the .NET Framework, Silverlight, .NET for Windows Store apps, Windows Phone, and Xbox 360, and provides a Visual Studio template that you can use to build assemblies that run without modification on these platforms. If you don't use a Portable Class Library project, you must target a single app type, and then manually rework the class library for other app types. With the Portable Class Library project, you can reduce the time and costs of developing and testing code by building portable assemblies that are shared across apps for different devices.
To help us refactoring the code to support this, I found this great tool: PCL Compliance Analyzer. Select an assembly file, set of platforms you want to target, and it will show you if the assembly is PCL compliant and what calls are not. Here are the results for Mono.Cecil for example: