3. Breaks up large chunks of functionality into smaller pieces Allows the teams to work in parallel Allows to deliver additional functionality by 3rd parties Isolation – if a plugin crashes, the rest of the app keeps working Plug-ins Modules Managed Addin Framework
4. Design pattern Creates graphs of objects Manages dependencies between objects Manages lifetime of the objects Dependency Injection P&P Unity 2.0 public SampleViewModel( IShell shell, ISampleView view, IEventAggregator eventAggregator, IPersistenceFacade persistenceManager, ILoggerService loggerService, IExceptionManager exceptionManager, IWindowManagerExt windowManager) { ... } Autofac Ninject Castle
5. IoC + MAF = MEF ? Managed Addin Framework IoC Container Managed Extensibility Framework
6. An extensible framework for composing applications from a set of loosely-coupled componentsdiscovered and evolving at runtime Applications are no longer statically compiled, they are dynamically composed(Recomposition) Supported in BCL 4.0 and Silverlight 4 Available for .NET 3.5 / SL 3 (Codeplex Drop 9) MEF 2 Drop 2 available for download! Lives in the System.ComponentModel.Composition.dll SL has also some additional stuff in the System.ComponentModel.Composition.Initialization.dll Managed Extensibility Framework
9. PartDefinition is a blueprint for a Part(similar to .NET Type and Object) Part represents the exported value Parts and their definitions. Object GetExportedValue() import import import Part export export import import CreatePart() PartDefinition PartDefinition export export
11. Importit. public class Program { [Import] public ILogger Logger { get; set; } private static void Main() { var p = new Program(); p.Run(); } } Program ILogger Import
13. Composeit. import import import import import import import part part part part import import export export export export Composition Container part part part part part part
16. Compose it. private void Run() { var catalog = new AssemblyCatalog(...); var container = new CompositionContainer(catalog); container.ComposeParts(this); Logger.Info("Hello World!"); } Program Compose
26. Exportit. Metadata. [Export(typeof(IWidget))] [ExportMetadata("Location", WidgetLocation.Right)] public partial class TwitterWidget : ITwitterWidget { [Import] public TwitterWidgetPresentationModel PresentationModel { get; set; } } Twitter Widget Put me on the right Export IWidget
27. Importit. Metadata. [Export] public class ShellPresentationModel { [ImportMany] public Lazy<IWidget, IWidgetMetadata>[] Widgets { get; private set; } } ShellPM Collection of Lazy IWidgets with IWidgetMetadata Import
29. Exportit. In a customway. [Export(typeof(IWidget))] [ExportMetadata("Location", WidgetLocation.Right)] public partial class TwitterWidget : ITwitterWidget { [Import] public TwitterWidgetPresentationModel Model { get; set; } } Twitter Widget Put me on the right IWidget Export
30. Exportit. In a customway. [Widget(WidgetLocation.Right)] public partial class TwitterWidget : ITwitterWidget { [Import] public TwitterWidgetPresentationModel Model { get; set; } } Twitter Widget Put me on the right IWidget Export
32. Recomposition. Parts introduced to or removed from the container may have an impact on this import – a part can opt-in to allow this recomposition. part Compose() part part? part CompositionContainer Catalog Catalog Catalog PartDefinition PartDefinition PartDefinition PartDefinition
33. Recomposition. [Export] public class ShellPresentationModel { [ImportMany(AllowRecomposition = true)] public Lazy<IWidget, IWidgetMetadata>[] Widgets { get; private set; } } ShellPM Collection of Lazy IWidgets with IWidgetMetadata Import
35. Stable composition. Parts with missing required imports are rejected. part requires zero or more requires part part requires part part requires missing
42. A set of extensions developed by community Where can I find it ? www.mefcontrib.com www.mefcontrib.codeplex.com http://github.com/MefContrib/ MefContrib MefContrib-Samples MefContrib-Tools MEF Contrib
43. InterceptingCatalog– enables interception ConventionCatalog– conventions based programming model FilteringCatalog – enables parts filtering based on any criteria GenericCatalog – enables support for open-generics FactoryExportProvider – factory based registration IoC integration layer – MEF / Unity MefContrib – what’s in it for me?
47. MEF ships with Attributed programming model Programming models are extensible Programming models. MEF Primitives ReflectionModelServices ExportDef PartDef ImportDef
48. + Ease of programming + Resolves dependencies between components + Automatic component discovery + Can compose types, fields, props and methods - Slower than the IoC containers - Lack of some IoC features Method injection Assisted injection Lifetime management - No component separation (separate appdomain, process) MEF vs IoC vs MAF
49. Managed Extensibility Framework http://mef.codeplex.com/ MEF in MSDN Magazine http://msdn.microsoft.com/en-us/magazine/ee291628.aspx MEF Contrib http://mefcontrib.com/ Glenn Block’s Blog http://blogs.msdn.com/b/gblock/ Piotr Włodek’s Blog http://pwlodek.blogspot.com/ Useful links
Editor's Notes
We are gonna talks about MEF, and how to write EXTENSIBLE applications!
DI is a design pattern in witch a special entity, usualy a container, is responsible for creating and managing the graph object.If you were to create the instance yourself you would have to inject all dependencies yourself.
MEF combines the best features of the IoC frameworks with MAF
Composable part is MEF’s representation of a class instance.
MEF out of the box ships with the Attributed Programming Model.
MEF composes available parts together.
MEF doesn’t allow to create parts in inconsistent state.
