What Impact Will Entity Framework Have On Architecture

What impact will the Entity Framework and Entity Data Model have on application architecture?
Eric Nelson
Microsoft UK
Blog: http://geekswithblogs.net/iupdateable
Twitter: http://twitter.com/ericnel and http://twitter.com/ukmsdn
Podcast: http://bit.ly/msdnpodcast
Newsletter: http://msdn.microsoft.com/en-gb/flash
Slides, links and background “diary” posts can be found on my blog

Agenda
ORM Overview and Impact
Entity Framework V1 recap
Entity Framework V4 overview
Impact of embracing Entity Framework

ORM Overview
“Not your fathers ORM”

Why did the industry create ORMs?
We started with data in the 70s
The first RDBMS were data centric
Overtime they received bolt ons for behaviour
In the late 90s, programming became object centric
Rise of OOP and OOD
Behaviour
The two approaches didn’t play nice
“impedance mismatch”
Different type systems
Different emphasis
Set vs Graph theory
Many to Many

One approach – the Object Database

The “winning approach” – Object Relational Mapping
Technique for working with relational data as if they were objects in memory
Hide away the complexity of the underlying tables and give a uniform way of working with data
An Abstraction
RDBMS is about data
OO is about data + behaviour

What good comes from adopting an ORM
Developer productivity
Less code
Better code than the “average” developer
Better database code than the “average” developer
Retain database independence

ORM and Code Gen
ORMs are highly configurable code gen tools
Made normally by someone else
We like code gen
Helps with DRY
But we sometimes dislike ORMs
As they can break YAGNI
And they often are “leaky”
And we didn’t write them
And they aren’t perfect for what we have in mind

ORM is not...
The answer to life the universe and everything
The absolute fastest way to do everything
Supported by many reporting tools
Always in step with RDBMS advances

ORM is the Vietnam of Computer Science
Ted Neward
“there is no good solution to the object/relational mapping problem”
Painful tradeoffs
Proposed “Integration of relational concepts into the languages”

Impact of adopting an ORM

Impact of adopting an ORM
Start with Behaviour or start with Data?
Code firstor Map first?
Database Independence but at what cost?
Always access via the ORM?
No behaviour in the database?

Behaviour in the database?
RDBMS can model data and behaviour
Stored Procedures
Triggers
Views
User defined types
Some RDBMS better than others
SQL Server 2005/2008 can run .NET code and you can extend the type system.

Stored Procedures are evil?
From the world of Java
All about portability and vendor neutrality
Stored Procedures were hard to port
ANSI SQL std doesnt includes SPs
Therefore don’t use Stored Procedures
This is changing...
From the world of .NET
Overuse
Incorrect use
Lead to “no sps here”

Stored Procedures and ORMS
Some ORMs offer little or no support
Some offer great support
CUDvs CRUD
Functions
Still a great choice
Can solves identified performance bottlenecks
Bulk data manipulation
Maintenance operations
Multiple applications to the same database
Security (hmmm....)

ADO.NET Entity Framework v1.0
It arrived slightly under cooked 

ORM on the Windows Platform
Many ORMs out there
No clear “winner” = relatively little adoption of ORM
Developers waiting on Microsoft

The future of ORM on Windows
Entity Framework and LINQ to Entities is our strategic technology
Big investment into Entity Framework 4.0 in VS2010
Best of LINQ to SQL moves into LINQ to Entities
Microsoft is using it
Data Services - shipping
Reporting Services
more
Partners supporting it
Database Vendors – IBM,OpenLink, DataDirect, Devart etc
ORM vendors supporting it
Entity Framework is not just about ORM

ADO.NET Entity Framework
Tools and services to create an Entity Data Model (EDM)
Tools and services for consuming an Entity Data Model

Entity Data Model
Entity Data Model
Application model
Mapped to a persistence store
Comprised of three layers:
Conceptual (CSDL)
Mapping (MSL)
Storage (SSDL)
Database agnostic
Comprised of:
Entities
Associations
Functions
Conceptual
Mapping
Storage

Consuming the EDM
1
2
The ORM
- optional
Object Services
3
Entity Client

Demo: Entity Framework

LINQ recap
“Bringing relational into the languages”
Eliminating the impedance mismatch (No... Not really )
LINQ to SQL is like C# to C++
Tidy, Composable, Associations, Shaped results, Parameterization, Client processing
http://linqpad.net/WhyLINQBeatsSQL.aspx

An absolutely fantastic release. Did you like it?

An amazing release. Who could have thought 3.0 could beat 2.0!

And in Visual Studio 2010 and .NET Framework 4.0 we get our fourth release building on the success of 1.0, 2.0 and 3.0 

Lots of new features
Better Tools and Design Experience
More powerful/flexible runtime
And
N-Tier
Persistence Ignorance
Code Only

Better Tools and Design Experience
Templated code generation
Model First
Stored Procedures
Pluralization
Complex Types
Better delete and search

More powerful/flexible runtime
Deferred Loading (aka lazy loading)
Foreign Keys surfaced
More complete LINQ implentation
ExecuteStoreQuery
EntityFunctions and SqlFunctions
Improvements to generated SQL

N-Tier
Self Tracking Entities

First class support for Persistence Ignorance
No modifications to your classes!

Code Only
Create the database from the classes
No model
Convention to config

Demo: Code Gen, MODEL First, SPs, Persistence Ignorance …

Architecturally impactful
Improved Code Generation
Mode First
Stored Procedures
EntityFunctions and SQLFunctions
Self Tracking Entities
Code Only

In Summary

Objects trump Tables
Use LINQ
Use an ORM
I don’t really care which. But Nhibernate and Entity Framework are good candidates
Use an ORM wisely

Resources
Slides, links and more
http://geekswithblogs.net/iupdateable
Entity Framework 4.0 Resources
http://bit.ly/ef4resources

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What Impact Will Entity Framework Have On Architecture

by Eric Nelson on Sep 24, 2009

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