Applied Entity FrameworkDaniel SimmonsDev ManagerMicrosoftSession Code: DTL401

Agenda

GoalsPriority 1: Increase success with the EF nowPriority 2: Prepare for what is coming in EF4

Approach: Create an EF N-Tier Web ApplicationSketch architectureBuild EF data access layer and business objectsCustomize code generation to add OnValidateCreate fake repository and web applicationAdd WCF service and real repository

Target Architecture

DB & Service Tier• Data Access Layer• Business Objects• WCF Service

Web Server• WCF Client• Business Objects• Web UI

Browser

Architectural Considerations

Know what tiers are needed and whyTier may have multiple layers

Sample mid-tier has DAL, business objects and serviceSample web-tier has repository, business objects and UI

Sample separates web-tier from mid-tier because…Reduces internal network surface exposed to the DMZCreates option for web-tier scale out

Consider service operations and payload shapesFactors include change rates and trust boundariesSample uses custom services and shared entities

Mid-Tier Persistence

Entity Partial Classes

EntityFramework

Context Entities

DAL Business Objects

Generated

Hand-Written

Demo #1: DAL and Business Objects

Look at an EF Model based on NorthwindExamine modifications for concurrency checksDebug optimistic concurrency in action

DAL and Business Objectsdemo

Demo 1 Takeaways

EF enables separate DAL and business object layers, but there is much less code to write

Hand-written DAL is replaced by combination of:EFstorage/entity mappinggenerated context

Business objects also generated, but extended with custom business logic

Pay attention to concurrencyEspecially in disconnected scenarios

T4

Output Text

Control CodeTemplate

Metadata

GeneratedCodeT4

Demo #2: T4 and OnValidate

Add T4 template to customize generated codeModify template for OnValidate mechanismAdd partial class with validation codeTest validation

T4 and OnValidatedemo

Demo 2 Takeaways

T4 makes customizing code generation easyEF4 will use T4 in a big way

Register SavingChanges event handler during context construction

EF4 makes SaveChanges virtualObjectStateManager tracks all changes

Use LINQ to Objects to interrogate itAvoid modifying other entities in OnValidate

Web Tier & Repository Pattern

Repository

Fake Impl

Real Impl

Web UIBusinessObjects

Demo #3: Fake Repository & Web UI

Add ICustomerRepository interfaceCreate fake implementationPull in Web UI written using the repository

Fake Repository & Web UIdemo

Demo 3 Takeaways

Mental model of a repository is an in-memory collectionCentralizes all data access in one place

Easy to understand and tune if neededDe-couples rest of application from data access

Easily create fake or mock implementationsEnables multiple real implementations

Did I mention that it de-couples the rest of your application from data access?

Cross-tier Communication

Persistence

WCF

Service

Web-tier

WCF Client

Repository

Mid-tier

SerializedEntities

Demo #4: Connecting the Dots

Turn ICustomerRepository into service contractExtend context class with AttachAsModifiedAdd implementation of service contractExamine EF disconnected updatesTest the implementationExamine web tier auto-proxy repositoryRun the final application

Connecting the Dotsdemo

Demo 4 Takeaways

Concurrency for disconnected operationsMaintain concurrency value from first read

Change-tracking for disconnected operationsIndividual property tracking often unnecessary

Disconnected graph manipulationMixed operations quite difficult in 3.5 sp1State transitions also constrained in 3.5 sp1Context operations treat graph uniformly

Improvements here in EF4 (APIs, Self-Tracking)

What Next?

Same patterns apply to .net 3.5 sp1 rich clientsEF4 POCO support adds many options

Completely separate business objects from DALSerialize business objects to Silverlight, .Net 2.0, …Additional flexibility in business logic and testability

Model-first enables generating DBCode-only removes need for separate metadata and mapping info

question & answer

More ResourcesCodeEF: http://msdn.microsoft.com/en-us/data/aa937723.aspx EF FAQ: http://blogs.msdn.com/dsimmons/pages/entity-framework-faq.aspxASP.Net MVC: http://www.asp.net/mvc

DocsSample: http://code.msdn.microsoft.com/dtl401sample T4 Templates: http://code.msdn.microsoft.com/t4ef35sp1

BlogsMine: http://blogs.msdn.com/dsimmons EF Design: http://blogs.msdn.com/efdesign ADO.Net Team: http://blogs.msdn.com/adonet

Related ContentBreakout SessionsDAT308 Design Patterns for Application Architecture with the ADO.NET EFDTL05-INT Surprise! It's the Entity Framework GotchasDTL312 The ADO.NET Entity Framework: Tips and Tricks

Birds of a FeatherBOF21 Solving the Unforeseen Challenges of the ADO.NET Entity Framework: How Can .NET Developers Get Better Prepared?BOF65 Implementing the Entity Framework in an n-Tier World

Hands-on LabsDTL20-HOL Application Development with the ADO.NET Entity Framework in the Microsoft .NET Framework 4.0

Track Resources

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© 2009 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS,

IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

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www.microsoft.com/teched Sessions On-Demand & Community

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www.microsoft.com/learning Microsoft Certification & Training Resources

Resources

www.microsoft.com/learningMicrosoft Certification and Training Resources

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Complete an evaluation on CommNet and enter to win!

© 2009 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS,

IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.