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Before we dig into the code for the web site, let's briefly recap the application's design I showed you in the two previous articles.

The following figure shows the four main components of the application: .

You saw how to implement the data access methods and database code and how the various classes were able to work together.

It builds on the foundation created in this first series, but digs much deeper into concepts like Validation, Sorting, Paging, Concurrency and Security. What should these objects be capable of and how do they look.

- I have written a new series on N-Layer design as a major follow up to this one. Part one dealt with the design of the application: what business objects do you need to fulfill the requirements of the application.

This means that the web site can consume objects like that are returned from the business layer that in turn got them from the data access layer.

In the middle of the diagram, you see the Business Logic Layer; the bridge between the web site and the data access layer.

It's the web site and the pages and code it contains that is the main subject of this article, as you have already seen the other three parts in the previous two articles.

In part two of the article series I showed you how the site was set up: the important layers each have a separate folder under the special , the site has a few other folders and files worth looking at.

The Bll gets instructions from the presentation layer (the web site in this example), to carry out tasks, like retrieving items from the data layer, or sending changed objects back into this layer.

Additionally, it can perform tasks like enforcing security and carrying out validation, as you saw in part two of this article series.

However, writing explicit code to work with your business objects isn't always fun, and can be a cumbersome task.

Therefore, this article (part three) deals with using the business objects in a web application. NET controls like the Grid View in conjunction with the business objects.

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