Intro Entity Framework

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Shawn WildermuthWildermuth Consulting Services

Microsoft MVP (C#), MCSDhttp://wildermuthconsulting.com

The Entity FrameworkAn Introduction


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Wildermuth Consulting Services Introducing the Entity Framework

Who Am I?

Shawn Wildermuth [email protected]

Wildermuth Consulting Services

http://wildermuthconsulting.com C# MVP, MCSD, MCT, INETA Speaker Book Author

Pragmatic ADO.NET MCTS Training Kit (Exam 536) MCPD Training Kits (Exams 547, 548 & 549) Programming WPF (Authored WPF/E Appendix only) Prescriptive Data Architectures Upcoming

Silverlight Tour (www.silverlight-tour.com)


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Agenda

The Problem Statement

The Entity Framework

Entity Data Model

Entity Client

Object Services

Entity SQL

LINQ for Entities


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The Problem

Analysts see the world in OR Diagrams:


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The Problem

Developers see the world in class diagrams:


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The Problem

DBAs see the world in ERDs



The Problem

Impedence mismatch of different models:

RelationalModels

Multiple Data

Services (UDM,SMDL)

OO Models

DomainModels

ApplicationLayering

Data models Extend up to themid-tier.

Application models abstractpersistent Stores



The SolutionThe Entity Framework

Object Services

Entity Client

Entity Data Model

ADO.NET Providers

LINQ for Entities



Demo



The Entity Framework

Not about Persistence

Not an Object-Relational Mapper per se

Not an Object Database

Not a Code Generator

It is about Services

Object Services

View Services Persistence Services



What is an Entity?

"A thing which can be distinctly identified

Peter Chin, 1976

"Any distinguishable person, place, thing, event, or

concept, about which information is kept

Thomas Bruce, 1992



Employee

EmployeeID = 729742LoginID = pete

Title = "Developer"

VacationHours = 0

ExpenseAccount =

CarLicenseNum =

What is an Entity (2)

Like an object Unlike an object

Known type

Distinct identity

Properties holding scalar values Properties holding references to

other entities

No methods

Entity identity determined from

entity (aka primary key) References to other entities

follow stylized patterns

Lives within a particular entity set

Employee

EmployeeID = 729742

LoginID = pete

Title = "Developer"

VacationHours = 0

ExpenseAccount =

CarLicenseNum =

SalesEmployeeEmployeeID = 729742

LoginID = pete

Title = "Developer"

VacationHours = 0

ExpenseAccount = true

EmployeeEmployeeID = 294272

LoginID = adam

Title = "Dev Lead"

VacationHours = 0

Reports Manager



What is the Entity Data Model?

The EDM is a schema language for entities:

Entity type definitions

Scalar types

Inheritance of entity types

Relationship type definitions

Containers

Simple and Complex Scenarios Hierarchies

Star Schemas

Universal Schemas

Employee

Int32 EmployeeID

String LoginID

String Title

Int16 VacationHours

Manager_Reports

Manager 0..1

Reports *

SalesEmployee

Bool ExpenseAccount



Entity Data Model (EDM)

ConceptualModel Mapping

StorageModel



EDM Conceptual Model

Defines the Entities



EDM Storage Model

Description of where/how stored:



EDM Mapping Layer

Maps Conceptual to Storage:



EDM Where are we?

The model is definedbut

Where are my classes?

Where is my project?

Help Calgon, take me away!

The EDM is simply the development of the model

Services are layered on top of the EDM

Including Building of Objects, Persistence, etc.



Entity Client

An ADO.NET Managed Provider for Clients

Connections, Commands, DataReaders

Exposes the Entity Model directly as data sourceusing (EntityConnection cn = new EntityConnection(cs))

using (EntityCommand cmd = cn.CreateCommand())

{

cn.Open();

cmd.CommandText = qry;

DbDataReader rdr = cmd.ExecuteReader(CommandBehavior.SequentialAccess);

while (rdr.Read())

{

Console.WriteLine(rdr[0]);

}

}


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Entity SQL

Entity SQL is a dialect of SQL for querying the EDM

Familiar SQL language

A full SQL Dialect

SELECT Contact.FirstName, Contact.LastName

FROM PersonModel.Contact as Contact

WHERE Contact.FirstName = 'John

SELECT VALUE Contact


WHERE Contact.FirstName = 'John'";

SELECT TOP 10 VALUE Contact


ORDER BY Contact.LastName


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Entity SQL

The real power is from model knowledge

Entity Graphs

Polymorphic Results

Real Set Operators

SELECT VALUE p FROM EntityNorthwindContext.Products as p

WHERE p.Category.Name = 'Beverages'

SELECT VALUE p FROM EntityNorthwindContext.Products as p

WHERE p is DiscontinuedProduct

(SELECT VALUE p FROM EntityNorthwindContext.Products AS p

WHERE p.UnitsInStock > 0)INTERSECT /* OVERLAPS, EXCEPT, UNION */

(SELECT VALUE p FROM EntityNorthwindContext.Products AS p

WHERE p.UnitsOnOrder > 0)


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Object Services

Used to expose EDM to Code

Code Generation for Entities

Object Queries

Change Monitoring


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Code Generation

New Models by default create an object model

Entities include data, not behavior

Generated Code derives from EntityObject by default

Full Conceptual Model is generated

Can do IPOCO if needed

POCO might be supported (i.e. nHibernate) eventually


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Code Generation (2)

Entity Classes:


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Code Generation (3)

Context Class

Used to represent bundle of service objects

E.g. Connection, StateManager, etc.


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Querying with Classes

ObjectQuery is used to issue Entity SQL Queries

Supports polymorphic searchesusing (PersonModel ctx = new PersonModel())

{ ctx.Connection.Open();

string qry = @"SELECT Contact



ObjectQuery query = new ObjectQuery(qry, ctx);

ObjectQueryResult results = query.Execute(MergeOption.NoTracking);

List list = results.ToList();

}

using (PersonModel ctx = new PersonModel())

{ ctx.Connection.Open();

string qry = @"SELECT Contact



ObjectQuery query = new ObjectQuery(qry, ctx);

ObjectQueryResult results = query.Execute(MergeOption.NoTracking);

List list = results.ToList();

}


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Modifying Data

Changes can be made directly to Entities

Context is used to save changesusing (PersonModel ctx = new PersonModel())

{ // ...

List contacts = results.ToList();

Contact firstContact = contacts[0];

firstContact.Title = "Mr.";

int changes = ctx.SaveChanges();}


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LINQ to Entities

Language Integrated Query over Entitiesusing (PersonModel ctx = new PersonModel())

{

ctx.Connection.Open();

var results = from c in ctx.Contact

where c.FirstName == "John"

select c;

List contacts = results.ToList();

theList.DataContext = contacts;

}


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LINQ for SQL?

Why LINQ for SQL and Entity Framework?

Its not about code generation!

Its about gaining intelligence about a data model

EF is not for RAD/Prototype solutions

Building an intelligent model is worknot drag-n-drop

Entity SQL is what makes it better for mature projects


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Entity Framework Links: My Website (www.wildermuthconsulting.com)

My Blog (www.adoguy.com)

Presentation and code available there

My E-mail ([email protected]) ADO.NET Team Blog (blogs.msdn.com/adonet/)

Orcas ADO.NET Forums

(http://forums.microsoft.com/MSDN/ShowForum.aspx?ForumID=533)

Intro Entity Framework

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