Guide to Entity Framework with

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Here's exactly where an
ORM fits in. The figure given next shows how objects in 
an application can be mapped to the relational store by using a mapping layer. 
This mapping layer is provided by the ORM. An ORM is a method of representing 
the relational tables as entities in the object world. ORMs came onto the market to 
provide you with a framework using which you can connect your applications to the 
underlying database without having to write much code. Most importantly, you can 
use ORMs to connect to any database, increase development productivity, ensure 
database independence, and database portability.
Objects in
Memory
Object
Object
Object
Object
Object
Object
Object
Object
Object
Mapping Logic
Relational Database
O/R Mapping

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Chapter 1
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To bridge this apparent mismatch between the data and the object models, ORM 
tools have evolved. They are used to reduce the code required to transform your 
application's business objects into a form that can be persisted into the relational 
store and vice-versa.
ORM
Database
Read( )
Write( )
Objects B
Read( )
Write( )
Objects A
Microsoft first released its ORM by the name of 
LINQ to SQL, which shipped with 
.NET Framework 3.5 and Visual Studio 2008. However, LINQ to SQL was restricted 
to working with SQL Server databases only. Entity Framework is an attempt by 
Microsoft to provide you with an extended ORM built on top of the ADO.NET 
provider model and enable you to connect to and work with any database.
What is the ADO.NET Entity Framework?
Entity Framework is a type of ORM. It is a development platform that provides a 
layer of abstraction on top of the relational or logical model. In doing so, it isolates 
the object model of the application from the way the data is actually stored in the 
relational store. Developers can use the ADO.NET Entity Framework to program 
against an object model rather than the logical or relationship model. 

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Introducing the ADO.NET Entity Framework