Managed Extensibility FrameworkBart J.F. De Smetbartde@microsoft.comhttp://blogs.bartdesmet.net/bartSoftware Development EngineerMicrosoft CorporationSession Code: DTL315

Agenda

Why extensibility mattersExtensibility the naïve wayMEF versus System.AddinCore conceptsLots of demosSummary

Extensibility in pictures

Source: http://www.gambiastart.nl

Customer versus developer

Source: http://www.insidefurniture.com Source: http://cristinalaird.files.wordpress.com

Extensibility is hard Looks familiar?

Too hard?

Take a step backinterface IMathBinOp{ string Name { get; } int Calculate(int a, int b);}

IMathBinOp GetOperation(string path, string type){ Assembly asm = Assembly.LoadFrom(path);

return (IMathBinOp)Activator.CreateInstance( asm.Name, type );}

Contract

Dynamic load

Name the 10 problems…

Extensibility the naïve wayBart J.F. De SmetSoftware Development EngineerMicrosoft Corporation

demo

Agenda

Why extensibility mattersExtensibility the naïve wayMEF versus System.AddinCore conceptsLots of demosSummary

Managed Extensibility Framework

Partshave a contract

are found in a catalog

compose in a container

Square with 4 pins

I have these blocks

Let’s build something

System.Addin in a nutshellCross-

process or appdomain

Versioning adaptation

The essence of an add-in

Is System.Addin overkill?

System.AddinIsolation boundariesActivation of add-insAcross CLR versions

MEFComposition engine at its coreUtilities for discoverySimple declarative model

Answer: complimentary technologies

Agenda

Why extensibility mattersExtensibility the naïve wayMEF versus System.AddinCore conceptsLots of demosSummary

A world of give and take

Import

Export

Composed

“I need” “I have”

Composition

Host application

Need a IMathBinOp

Extension A

Have a IMathBinOp

MEF composition

engine

[Export] [Import]

Part

Part

Import and Export in practiceinterface IMathBinOp{ string Name { get; } int Calculate(int a, int b);}

class Calculator{ [Import] public IMathBinOp Operator { get; set; }}

[Export(typeof(IMathBinOp))]class Add : IMathBinOp{ // Implementation}

Contract

Import

Export

Host applicationExtension

How to compose?

CompositionContainerWiring “surface” where magic happens

CompositionBatchContains the parts to be wired together

ContainerBatch

PartCompose

Import and Export in practiceclass App{ static void Main() { var calc = new Calculator();

using (var container = new CompositionContainer()) { var batch = new CompositionBatch(); batch.AddPart(calc); batch.AddPart(new Add()); container.Compose(batch); }

var res = calc.Operator.Calculate(1,2); }}

Manual composition

Simple compositionBart J.F. De SmetSoftware Development EngineerMicrosoft Corporation

demo

Advanced topics in import/export

Named contractsTypically based on TypeCan also be string-based

ImportManyFor use with collectionsE.g. calculator has many operations

Instantiation controlWhich constructor to run?Part creation policies (sharing of instances)

Where do parts come from?

Concept of a catalogType catalog – explicit list of typesAssembly catalog – attributed types in an assemblyDirectory catalog – based on directory searchAggregate catalog – allows combining catalogs

Union operation

ComposablePartCatalog base classQueryable for parts (Parts)Search exports for a given import (GetExports)

Using a DirectoryCatalogclass App{ static void Main() { var calc = new Calculator();

var catalog = new DirectoryCatalog(EXTPATH); using (var container = new CompositionContainer(catalog)) { var batch = new CompositionBatch(); batch.AddPart(calc); container.Compose(batch); }

var res = calc.Operator.Calculate(1,2); }}

Search path

Working with catalogsBart J.F. De SmetSoftware Development EngineerMicrosoft Corporation

demo

Agenda

Why extensibility mattersExtensibility the naïve wayMEF versus System.AddinCore conceptsLots of demosSummary

Selection of MEF Preview 6 samplesBart J.F. De SmetSoftware Development EngineerMicrosoft Corporation

demo

http://mef.codeplex.com

Agenda

Why extensibility mattersExtensibility the naïve wayMEF versus System.AddinCore conceptsLots of demosSummary

The ABC CCC of MEF

Extensibility

Compose

CatalogContract

question & answer

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