Read original post by Kim Schmidt at Vnext.org
The development of business applications is similar to a building construction. If we put bricks and cement mortar together without following a well-defined pattern, we will move forward quickly but, sooner or later, we will face serious problems, and eventually the building may have to be evacuated.
Here we will show you how to build solid applications using the recommended pattern for Silverlight and WPF that is, MVVM. For its implementation, we will use the well-known library MVVM Light Toolkit (available at http://mvvmlight.codeplex.com/). Finally, we will see how to decouple the different modules of our application via Managed Extensibility Framework (MEF).