How and When to Use MEF: Too Much Is Never Enough

1. SESSION CODE: DEV304 How and When to Use MEF: Too Much Is Never Enough Jon Flanders Title MCW Technologies

2. Managed Extensibility Framework (MEF) • MEF is a framework for creating loosely-coupled, extensible applications • This has always been possible with .NET • Interfaces+classes+dynamic assembly loading • MEF is a standardization of this pattern • Much of Visual Studio 2010 uses MEF • Its extensibility layer relies on it heavily

3. MEF in a nutshell • MEF centers around three main concepts • Catalog • Exports • Imports • Catalogs contain components that are to be composed • Exports expose “Contracts” • Classes or properties • Imports are properties that require Exported instances • Composition pulls it all together

4. MEF in action NameTitleCompany DEMO

5. MEF Basics… Export it. Import it. Composeit.

6. Export it. [Export(typeof(UserControl))] public class Widget1 : UserControl { public string Message { get{return(string) Button.Content;} set{Button.Content=value;} } } Widget1 UserControl Export

7. Import it. [Export(typeof(UserControl))] public class Widget1 : UserControl { [Import] public string Message { get{return(string) Button.Content;} set{Button.Content=value;} } } Widget1 String Import

8. Import it. [Export(typeof(UserControl))] public class Widget1 : UserControl { [Import(“HelloMEF.Message”)] public string Message { get{return(string) Button.Content;} set{Button.Content=value;} } } Widget1 “HelloMEF.Message” Import

9. Import it. [Export(typeof(UserControl))] public class MainPage: UserControl { [ImportMany(typeof(UserControl))] public IEnumerable<UserControl> { get;set; } } Main Page UserControl ImportMany

10. Compose it. PartIntializer: “Compose yourself” public MainPage() { InitializeComponent(); CompositionInitializer.SatisfyImports(this); } MainPage Compose

11. MEF in an application NameTitleCompany DEMO

12. Resources Learning • Sessions On-Demand & Community • Microsoft Certification & Training Resources www.microsoft.com/teched www.microsoft.com/learning • Resources for IT Professionals • Resources for Developers • http://microsoft.com/technet • http://microsoft.com/msdn

13. Related Content • Interactive Sessions • DEV05-INT | What's Wrong with My .NET Extensible MEF Application? • Session Type: Interactive Session • Thursday, June 10 | 8:00 AM - 9:15 AM | Rm 347 • Track: Developer Tools, Languages & Frameworks • Speaker(s): Daniel Plaisted • Level: 300 - Advanced • Hands-on Labs • DEV06-HOL | Introduction to Managed Extensibility Framework

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