Jeff DerstadtSenior Development LeadMicrosoft Corporationjeffders@microsoft.com

Entity Framework Deep Dive

Patterns & Architecture

AgendaRepository pattern in MVCBetter testabilityBuilding N-tier ApplicationUsing Stored ProceduresCode First Programming

Mult

i Ti

er

Sin

gle

Tie

r

Separation of concernsCentralize and encapsulate data access codeIsolate upper layers from data access infrastructureProvide greater control over data access

Repository Pattern Goals & Benefits

User Interface

Data Access Layer

Database

Web Silverlight

New Data Access LayerData Access Layer

Fake Database

Business Logic / Controller

Repository is a class with data access methodsEncapsulates query and update operationsExposes entity classes with persistence ignorance

Often used with the UnitOfWork patternEncapsulates transaction and save operations

Repository Pattern Overview

public class BlogRepository{ public BlogRepository(IUnitOfWork unitOfWork) { ... }

public IEnumerable<Blog> GetAllBlogs() { ... }

public void AddPost(Post post) { ... }}

Best PracticesWrap the ObjectContextCreate separate repositories for each aggregate rootMultiple repositories can share same ObjectContext as a unit of workQuery methods return IEnumerable<T>Repository interface is a strong contract

Common AlternativesQuery methods return IQueryable<T>Repository<T> base class

Repository using Entity Framework

Repository using Entity Framework

Demo

Goal: swap out the data access code with something in-memory

It’s fasterYou have more control

Two approachesFake your derived ObjectContext

Build an interface BlogContext IBlogContextUse IObjectSet

It’s IQueryableIt’s updateable (AddObject, DeleteObject, etc.)It’s testable because you can implement your own

Fake your Repository

Entity Framework Testability

Entity Framework Testability

Demo

N-Tier Options

Low HighComplexity

DataSetData

Transfer Objects

High

Interoperabilit

y

??Self-Tracking

Entities

T4 Templates – can create a template that generates default DTOs for each entityForeign Keys –Manage relationships using scalar valuesAbility to set current and original values

For the whole entityApplyCurrentValuesApplyOriginalValues

For member values

ChangeObjectState – change the state of an entityChangeRelationshipState – change the state of a relationship

Data Transfer Objects in EF 4.0

EF 4.0 introduces self-tracking entitiesIt’s easy to:

Get started: Add the entity template to your projectMake changes: Just work with your objectsPersist changes: Call one method, ApplyChanges

Entities have no dependencies on EFEntities track their own changes as they happenWire-format enables services to be used on other platforms like Silverlight and Java

Achieving Low Complexity

Self Tracking Entities

Demo

You are communicating across tiersYou want to persist your change-setYou need more control over your entities on the client and/or the serverYou need more control over your service implementation

When to use self-tracking entities

Now available in the designerCan map one or more of

SelectInsertUpdateDelete

Still not there, but planned in the next releaseMultiple result setsTVFs

Stored Procedures

Stored Procedures

Demo

WhenDatabase is an implementation detailModels are overheadJust let me code!

Code First is where you startAvailable as a CTP for VS 2010 and .NET 4.0http://www.microsoft.com/downloads/

Code First

Code First

Demo

Code First is a work in progressAvailable post .NET 4.0Planned additions

Conventions, conventions, conventionsPrimary keys and store generated patternsRelationship inversesForeign key constraintsReachabilityComplex types

Data annotation attribute support (existing and new)Improved APIBetter integration (OData, WCF RIA Services, ASP.NET, etc.)

Code First

New features for SQL ServerEnum supportCustom types (UDTs) such as spatialTVFsAlternate keys

New features for performance and scalabilityLarger model supportIncremental model loadingScalable design surface

New features for productivityEnhanced API for Code FirstMore control over entity shape (type transformations, fields, factory methods)More control over change tracking and validationBuilt-in logging and tracing

The Road Ahead

Use the Repository pattern and wrap the ObjectContext to achieve better seperation of concernsBuild better unit tests by faking your ObjectContext and ObjectSetsUse self-tracking entities as a low complexity, higher interoperable N-tier solutionImproved stored procedure support in EF4CodeFirst is coming and allows you to build models with code

In Summary

Thank you for your Attention!For more Information please contact

Jeff DerstadtSenior Development Lead

jeffders@microsoft.com425-706-9683

Microsoft Corporation1 Microsoft WayRedmond, WA 98052 USA

http://msdn.microsoft.com/data

Gives us feedbackhttp://blogs.msdn.com/adonethttp://blogs.msdn.com/efdesign