Validation ASP.NET Controls
An important aspect of creating ASP.NET Web pages for user input is to be able to check that the information users enter is valid. ASP.NET provides a set of validation controls that provide an easy-to-use but powerful way to check for errors and, if necessary, display messages to the user. The topics in this section describe the validation controls and how to use them.
For complete syntax information for Web server controls, see Web Server Control Syntax.