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At the top of the diagram, you see the Web Site, the presentation layer of this application.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.
You'll find the download link at the end of this article.In the middle of the diagram, you see the Business Logic Layer; the bridge between the web site and the data access layer.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.In the Download for this application you also find the SQL Scripts to recreate the database on SQL Server 2000 or SQL Server 2005.The , while the other points to a database on a commercial version of SQL Server 2000 or 2005.Additionally, it can perform tasks like enforcing security and carrying out validation, as you saw in part two of this article series.
The data access layer contains the code that directly interacts with the data source, a SQL Server database in the case of the Contact Person Manager application but this could be any other kind of data source, like text or XML files, Access, Oracle, DB2 databases and any other data source you can come up with.
To display a list of users in a will be quite plain, with black text on a white background.
Although the ASPX page only needs 11 lines of code, a lot of other code is executed under the hood.
The following figure shows the four main components of the application: .
They don't have any behavior, and can therefore be considered as "dumb" objects.
With the additional files in the site looked at, let's take a look at how you can display contact persons on a page.