ADO.NET Entity Framework

MD. SAIFULLAH AL AZAD, Software Architect LEADS Corporation Limited

April 22, 2023

ADO.NET ENTITY FRAMEWORK

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What Is It?

Visual Studio 2010.NET 4.0LINQEntity Framework 4.2

The ADO.NET Entity Framework is part of Microsoft’s next generation of .NET technologies.

It is intended to make it easier and more effective for object-oriented applications to work with data.

SQLServer

SQLAzure

Visual Studio “Quadrant”

SQL Server Modeling Services

Entity Framework

ADO.NET “M”/EDM

Data Services

…

Architecture

The Logical Data Model• Almost any business

application today has to speak to a relational database.

• This involves the usual suspects of tables with foreign keys, a smattering of views, and generally a gob of stored procedures.

Tables

Views

Stored Procedures

Foreign Key Relationships

The Object-Oriented Domain Model

Objects

Behavior

Properties

Inheritance

Complex Types

Applications themselves are written in a completely different world.

The same data that lives in the relational database is represented entirely differently in the application.

The ResultLogical Data Model

Lots of Custom Code

Application Domain

The result of this “impedance mismatch” is that developers devote a lot of time and energy writing code to translate between how the database likes to see data and how the application likes to see data.

Other Ways to Address The Same Problem Hibernate (Java) Enterprise Objects Framework

(Mac OS) NHibernate (.NET) LINQ to SQL (Visual Studio 2008) And many, many, more …

The ADO.NET Entity FrameworkLogical Data Model

Entity Data Model

Less Custom Code

Application Domain

The ADO.NET Entity Framework seeks to remedy the problem by providing a layer of abstraction between the logical data model and the application domain.

Why the Entity Model?Logical Data Model• Tables• Rows• Foreign Keys

Entity Data Model• Entity Sets• Entities• Relationships

Closer to the application problem space

Better suited for object oriented programming

Supports Inheritance Supports complex types Relationships are more

meaningful to the application

The “Stuff” in ADO.NET Entity FrameworkThe tools and technology that developers will interact with

when using the ADO.NET Entity Framework

Entity Data Model A gob of XML that

defines Logical Data Tables,

Views, Foreign Keys Entity Objects that

Map to the Logical Data

The Mapping Between the Two

Entity Data Model Designer A Visual Studio

Designer that protects developers from the XML that is the EDM

ObjectContext A code-generated

data context created from the Entity Data Model

Responsible for managing communication between the conceptual data model and the logical data model

Entities Code-generated

class definitions for objects defined in the EDM.

Getting the Data OutHow do we get data out of the fancy Entity Data Model?

eSQL (Entity SQL) A brand new SQL

language to learn Leverages the rich,

object-oriented Entity Data Model Inheritance Collections Complex Types

Literal Strings – No Compiler Checking

Questionable value in embedded SQL in code

Extensions Methods and String Predicates Queries the object

model created against the EDM

Still string-based. No compiler checking

An ugly mix of code and eSQL statements

LINQ to Entities Full compiler

checking. No wondering if the query is valid.

A fun new SQL-Like syntax

More OO-ish

What Can You Do?The power of the Entity Data Model contrasted to a logical

data model of tables and stored procedures.

Combine Multiple Logical Tables into One EntityDatabase Tables Entity Data Model

Implement InheritanceDatabase Tables Entity Data Model

Other Fun Stuff Implement Complex Types (e.g.

Address) Consume Conceptual Model with

Reporting Services and other BI Tools Create an EDM that talks to stored

procedures Use transactions, manage concurrency,

cache execution plans

Manipulate Data By Manipulating ObjectsDatabase Result Desired EDM Object ManipulationINSERT ROW Create new object

Add object to EDM ContextUpdate Context

DELETE ROW Get instance of object from EDM ContextAsk Context to remove the objectUpdate Context

UPDATE ROW Get instance of object from EDM ContextUpdate objectUpdate Context

New in ADO.NET Entity Framework 4.0 Model-first development Automatic pluralization Foreign keys in models POCO class support Lazy loading T4 Code Generation Template customization IObjectSet Virtual SaveChanges ObjectStateManager control

Self-tracking entities SQL generation

improvements More LINQ operator support LINQ extensibility ExecuteStoreQuery ExecuteStoreCommand SPROC import

improvements Model defined functions WPF designer integration Code-Only development

(Feature CTP)

App Code

Customers

ADO.NET

ProvidersSQL Server

Oracle

...

DataReader

Customers

Oracle

Command

Execute

Provider Specific (PL/SQL)

“SELECT * FROM CUSTOMERS”Customers

ADO.NET Today

Customers

Conceptual Model

UKCustomer

UKPremiumCustomer

Map

ADO.NET Entity Framework

App Code

Customers

ADO.NET

Providers*SQL Server

Oracle

...

Oracle

EntityProvider

DataReader

UKCustomer

Command

Execute

Conceptual Model

UKCustomer

UKPremiumCustomer

Map

Provider Agnostic (ESQL)

“SELECT * FROM UKCUSTOMER”

UKCustomer

ADO.NET Entity Framework

.NET Entity Provider (Entity SQL)

Command

ConnectionReader

EF

Store

.NET Data Provider

V2.0

Command

ConnectionReader

Adapter

EF

Conceptual Model

Entity Entityrelationship

Mapping (MSL)

EFProgramming Model

Object Relational Mapping

LINQ

ADO.NET Entity Framework

Store

Good Customers

IDFirstNameLastName

Bad Customers

IDForeNameSurname

Customers

CustomerIdFirstLastType

EntitiesMapping

Type=“G”

Type=“B”

Mapping Examples ( 1 – Splitting )

Store

Customer

CustomerId

First

Last

EntitiesMapping

CustomersID

FirstName

LastName

IsPremium

Overdraft

AccountManager PremiumCustomer

Overdraft

AccountManager

?

* Framework also supports TPT

Mapping Examples ( 2 – TPH )

Store

UkCustomer

CustomerIdName

EntitiesMapping

ClientView1select c.id, c.namefrom customers cwhere c.country = ‘UK’

p_DeleteUkCustomer

p_UpdateUkCustomer

p_InsertUkCustomer

Mapping Examples ( 3 – View + SPs )

Any Question