SAMS Teach Yourself ASP.NET in 24 Hours

Examining the Need for User Input Validation

In the past two hours, we've examined a number of ways to collect user input. In Hour 10, “Using Textboxes to Collect Input,” we saw how to use the TextBox Web control to collect text input; in Hour 11, “Collecting Input by Using Drop-down Lists, Radio Buttons, and Checkboxes,” we saw how to use DropDownList, RadioButton, and CheckBox Web controls to collect user input that was restricted to one or more items from a predefined list of items.

Typically, when collecting user input, we want the input to be in a certain format or conform to some set of guidelines. Input validation is the process of ensuring that the data entered by a user is in the proper format or meets certain constraints.

For example, ...