23.6. Validation Controls

This section introduces a different type of web control, called a validation control or validator, which determines whether the data in another web control is in the proper format. For example, validators can determine whether a user has provided information in a required field or whether a zip-code field contains exactly five digits. Validators provide a mechanism for validating user input on the client. When the page is sent to the client, the validator is converted into JavaScript that performs the validation in the client web browser. JavaScript is a scripting language that enhances the functionality of web pages and is typically executed on the client. Unfortunately, some client browsers might not support scripting or the user might disable it. For this reason, you should always perform validation on the server. ASP.NET validatio....