ADO.Net Entity Data Model Prerequisite

The following are the minimum pre-requisites to make use of ADO.Net Entity Data Model in your project.

.Net Framework 3.5  SP1

Visual Studio 2008 SP1
Make sure that you have Visual Studio 2008 SP1, ADO.Net Entity Data Model  Templates do        not come with the basic version of Visual Studio 2008, you need to have SP1 installed.

Targets Framework 3.5
Make sure that your Project is mapped to targets framework 3.5, you can check this is the Project Properties, in the Project properties window check that the Target Framework property is set to .net Framework 3.5 or Higher.

 
Latest versions like Visual Studio 2010 and 2012 have the ADO.Net Entity Data Model  Templates embedded from the basic version.

Another common thing which is overlooked is that the ADO.Net Entity Data Model Template is not a project type template, it is a file type template, means that you first need to create a project, then add ADO.Net Entity Data Model Template as one of the Items to the project.

Related Post
Concepts
ADO.NET Entity Framework
ADO.NET Entity Framework Architecture
Entity Data Model
LINQ To SQL Vs ADO.Net Entity Framework

Programming
ADO.Net Entity Data Model Prerequisite
Creating your First ADO.Net Entity Data Model
Selecting Data using ADO.Net Entity Framework
Selecting Data by Joining Tables using ADO.Net Entity Framework
Inserting Data using ADO.Net Entity Framework
Inserting Data with Foreign Key Reference using ADO.Net Entity Framework
Updating Data using ADO.Net Entity Framework
Updating Data with Foreign Key Reference using ADO.Net Entity Framework
Deleting Data using ADO.Net Entity Framework