Microsoft Visual Studio 2015 Unleashed, Third Edition

The Extensibility Problem

Before getting into the architecture and code-level details of MEF, it is useful to understand the problem or question that MEF is trying to answer. Put simply, that question is this: how can developers allow their applications to be easily extended by others, or conversely how can developers extend existing applications in a simple way?

A variety of hurdles have to be overcome in this space. For instance, how can an application be open for extensions yet closed so that its core functionality cannot be usurped against the intentions of its designers? What developers are really after is a consistent solution that enables dynamic applications to be created and thus enables other developers to extend those dynamic applications ...