What the heck is MEF?

1. What the heck is MEF? And why should I care? Jason Offutt Software Engineer Central Christian Church Email: jason.offutt@cccev.com Twitter: @JasonOffutt #RefreshCache

2. Managed Extensibility Framework • Originally an Open Source project started by Microsoft developers (mef.codeplex.com) • Now comes baked into .NET 4.0 • Included in System.ComponentModel.Composition

3. And I should care because? • It allows us to make our code more like Legos • Modular & pluggable • Encapsulated functionality • Not dependent on other components

4. So what can MEF do? • Act as an IoC container • Manage dependency injection without tons of configuration • Plays match-maker for your code “You use MEF to manage a set of unknown things. You use IoC containers to mange a set of known things.” – Glenn Block (MEF project manager)

5. How can Arena benefit from MEF? • MEF can simplify the way we do dependency injection • Less code to maintain! • No need for configuration in web.config or Arena Org Settings and Lookups • MEF will dynamically load the correct object based on the contract/interface declared at runtime • Allows for lazy-loading objects to delay expensive database calls

6. How can Arena benefit from MEF? • Allows us to keep our components very loosely coupled • Makes it easier to write testable code • Less energy required to engineer our own “seams” for unit testing. If you need a “fake” object, just use MEF to import it into your unit tests.

7. When can we use it? • It’s baked right into .NET 4.0 • When Arena supports .NET 4.0, it can be used anywhere • If you’re impatient, you can download the binaries for .NET 3.5 from mef.codeplex.com

8. Less talking, more code!