David Hill from the patterns & practices team posted a very interesting article concerning MEF and Prism. It talks about the benefits your applications get from using these extensibility technologies, but also clears some misunderstandings regarding their purpose. I’ve been faced with this question several times and the online community reflects this same common overlap. While MEF is purely an extensibility API, Prism is a development pattern that allows you to organize and manage your WPF/Silverlight project through modularity and thus isolate requirement and functionality concerns in development teams.

They’re both part of .NET Framework 4.0 and a MUST if you are developing big applications and/or needing your software to be extensible.

Check out the article here.

This is a nice one guys. I’ll give a nice overview about MEF, the Managed Extensibility Framework going on on codeplex. The Managed Extensibility Framework is a .NET library that enables greater reuse of applications and components. Using MEF, .NET applications can make the shift from being statically compiled to dynamically composed. If you are building extensible applications, extensible frameworks and application extensions, then MEF is for you.

Imagine the following scenario where you have an application that enlists and then shows a selected 3D vehicle. You have a ListBox with items in it, and by selecting an item, it renders a model on a 3D canvas of some sort. Now, suppose you want to be abe to abstract the type of operations/technologies going on on each vehicle rendering procedures. You want to give the possibility for different implementations, but with the same purpose. The best approach is for each vehicle to have it’s own assembly with it’s own unique logic, but in order for our main app to use it when calling for a render operation, it must implement a common interface. MEF allows us to dinamycally load and incorporate assemblies in your apps, so as long as they implement my interface, I am able to dynamically add more vehicles to my application after it is compiled running.

This is what MEF is all about. and there are some cool samples on this over the web so be sure to check them out.