Beginning ASP.NET 3.5: In C# and VB

Chapter 9. Validating User Input

So far you have been creating a fairly static site where you control the layout and content. At development time, you create your pages and add them to the menu so your users can reach them. You can make your site a lot more attractive by incorporating dynamic data. This data usually flows in two directions: it either comes from the server and is sent to the end user's browser, or the data is entered by the user and sent to the server to be processed or stored.

Data coming from the server can be retrieved from many different data sources, including files and databases, and is often presented with the ASP.NET data controls. You see how to access databases in Chapter 11 and onward.

The other flow of data comes from the user and is sent to the server. The scope of this information is quite broad, ranging from simple page requests and contact forms to complex shopping cart scenarios and wizard-like user interfaces. The underlying principle of this data flow is basically the same in all scenarios — users enter data in a Web Form and then submit it to the server.

To prevent your system from receiving invalid data, it's important to validate this data before you allow your system to work with it. Fortunately, ASP.NET 3.5 comes with a bag of tools to make data validation a simple task.

The first part of this chapter gives you a good look at the validation controls that ASP.NET supports. You see what controls are available, how to use and customize them, ...