Validation Controls
Dale Michalk, R. A. Cameron · Apress eBooks · 2004
Validation controls in ASP.NET are very popular with web developers. These controls are great time-savers because they eliminate the need to write repetitive code that checks user input. This is especially true when developers want to validate a user’s input on the client as well as on the server. Embedding validation JavaScript into the script code of an ASP page environment is not a task most folks volunteer for, so having built-in validation controls is a big step forward.