Summary

Validation controls in ASP.NET relieve the tedium of enforcing validation on a page. Simply placing a validation control on a page and pointing it to another control to validate provides both client-side validation for clients that support it and server-side validation each time the page is posted back. Four validation controls are provided for performing standard validation tasks such as checking that required fields have been populated , comparing the value of one field with another, verifying that the contents of a field fall within a given range, and performing a regular expression check on the contents of a field. Another control is available to generate a list of errors encountered on a page, either in paragraph summary form, as an alert dialog box, or both. Finally, if none of these controls perform the validation you need, a custom validation control lets you specify whatever validation algorithms you want on both the client and the server.