The following illustration shows the difference between a business-logic class that includes data-access logic without a repository and one that uses a repository.

You will begin by creating web pages in which the control to that class instead of to the repository class.

You can also download the application that is created by the complete tutorial series.

The Contoso University sample web application demonstrates how to create ASP.

For normal operation, you provide a repository object that works with the Entity Framework.

For testing, you provide a repository object that works with data stored in a way that you can easily manipulate, such as class variables defined as collections.

In this tutorial you will create separate classes for business logic and for data-access logic.

In the third tutorial in this series you will add sorting and filtering functionality to the application.This abstraction layer is implemented by creating an interface and using the interface when you instantiate the repository in the business-logic class.This makes it possible for you to provide the business-logic class with a reference to any object that implements the repository interface.Like the Getting Started series, this tutorial series uses the ASP. The control gives you more flexibility in other ways as well.NET Web Forms model and assumes you know how to work with ASP. Because you write your own data-access code, it's easier to do more than just read, insert, update, or delete a specific entity type, which are the tasks that the control is designed to perform.For example, you can perform logging every time an entity is updated, archive data whenever an entity is deleted, or automatically check and update related data as needed when inserting a row with a foreign key value. For example, when you update a department, you might need to validate that no other departments have the same administrator because one person cannot be administrator of more than one department.In some that includes both business logic and data-access logic.This tutorial series builds on the Contoso University web application that is created by the Getting Started with the Entity Framework 4.0 tutorial series.If you didn't complete the earlier tutorials, as a starting point for this tutorial you can download the application that you would have created.In the database diagram, right-click the table, and select Relationships.In the Foreign Key Relationships box click Add, then click the ellipsis for Tables and Columns Specification.The business logic class includes both business-logic methods and data-access methods, but the data-access methods call the repository to perform data-access tasks.You will also create an abstraction layer between your BLL and DAL that facilitates automated unit testing of the BLL.NET Web Forms applications using the Entity Framework 4.0 and Visual Studio 2010.The sample application is a website for a fictional Contoso University. To implement this architecture, you separate the presentation layer from the business logic layer (BLL) and the data access layer (DAL).