Learning ASP.NET 3.5, 2nd Edition

Chapter 4. Saving and Retrieving Data

So far, you’ve seen how to make functional web pages with clever and useful controls. You know how to change the appearance of the page in response to user selections, and how to use AJAX to enhance the performance of your application. But the applications you’ve made so far have been limited in what they can actually do. In this chapter, we add the most frequently sought-after functionality: the ability to retrieve, display, change, and store data.

Think about the web sites you visit most often, and you’ll find that almost all of them have one thing in common—they interact with persistent data. Persistent data is data that survives a single session; data that you expect will be there the next time you visit. In fact, it may even be data that can have significant financial consequences.

Shopping sites have databases to track their inventories and customer transactions. News sites keep databases with articles and photos in them, perhaps referenced by topic and date. Search engines use unimaginably large (and wicked-fast) databases.

Nearly every real-world commercial web application must be able to perform the four essential "CRUD” interactions with a database: Create, Read, Update, and Delete.

Fortunately, ASP.NET provides controls that make it easy and fast to perform these essential activities. We will demonstrate these interactions with SQL Server Express Edition (or its big brother, SQL Server) but they work equally well—or nearly so—with Microsoft ...