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I have read some documents about Entity framework, so i came to know that it makes entities like our database(ORM).

i tried to go deeper but i don't get satisfactory answer.

i want to know why and when entity framework is used? is LINQ necessary with this framework?

and the silly question is

what is the difference in "use" between 3-tier architecture and entityfrmaework ?

any related document will be helpful

thanks in advance.

Aijaz Chauhan
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    Entity framework is an ORM see [Why ORM is used](http://stackoverflow.com/questions/398134/what-are-the-advantages-of-using-an-orm). LINQ is for querying collections see [LINQ](http://msdn.microsoft.com/en-us/library/vstudio/bb397926.aspx). 3 tier architecture is usually Presentation Layer - Business Layer - Data Access Tier, Entity Framework usually work on Data Acess Tier. – Habib May 21 '13 at 06:32

1 Answers1

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i came to know that it makes entities like our database(ORM).

:-/

Actually EF will make entities that look like your DB model only if you decide to start with what we call DB First approach. Doing so, EF will somehow reverse engineer your DB model and create entities in an EDMX file that will become your business model. A best practice would be to change those generated entities and modify them in order to make them look like a real business model.

From my point of view, a DB model and a business model are two completely different things as they’re not designed for the same goal: DB model is designed to be able to persist and fetch DB data efficiently and business model’s goal is to conceptualize business needs and it must fit with how your application will manipulate it. The nice thing is that the EDMX is a 3 parts file with one distinct area for representing the DB model, one for the business/conceptual model and the last but not least: the mapping between the two! This allows you to have a "real" business model and be able to persit data in a completely different structure.

There is a LOT of documentation describing the different EF approaches; your starting point should be the ADO .Net site.

Here, you’ll find all the things you’ll need to get started including how to choose between the different approaches.

Now, for all your other questions:

i want to know why and when entity framework is used?

EF and other ORMs are used in order to create an abstraction layer on top of your DB. It lets you manipulate objects rather than accessing directly the DB. EF is the Data Access Layer (DAL) of your application and entities should be your business/domain model. One of the advantages is that it improve productivity by taking care of all the DB related code but on the other side, you’ll have to pay attention to what kind of T-SQL code will be generated dynamically. With an ORM it becomes really easy to generate ugly queries that lead to dramatic performances. Please search on google to find out the best practices and things to avoid when working with ORMs.

what is the difference in "use" between 3-tier architecture and entityfrmaework ?

As I said, EF is your DAL. So EF is somehow one of the tiers in your architecture.

Hope that helps!

MaxSC
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