I wrote this Code Project article about using MEF for extensibility in .NET. It's a good introduction.

There are other extensibility frameworks for .NET, such as SharpDevelop's Add-in Architecture, Mono.Addins and System.AddIn.

The general pattern is this:

• You define a contract (normally an interface) between the host and the extension
• You need a discovery mechanism that goes out and looks for installed extensions
• You need to be able to dynamically load the extensions and make the host aware of them

In practice it shares a lot with Dependency Injection and the Strategy Pattern.

I wrote this Code Project article about using MEF for extensibility in .NET. It's a good introduction.

There are other extensibility frameworks for .NET, such as SharpDevelop's Add-in Architecture, Mono.Addins and System.AddIn.

For Java, there is the Eclipse Plug-in Architecture.

The general pattern is this:

• You define a contract (normally an interface) between the host and the extension
• You need a discovery mechanism that goes out and looks for installed extensions
• You need to be able to dynamically load the extensions and make the host aware of them

In practice it shares a lot with Dependency Injection and the Strategy Pattern.