18.6. Performing Remote Validation

The last validation feature we will look at in this chapter is remote validation. This is a client-side validation technique that invokes an action method on the server to perform validation.

A common example of remote validation is to check whether a user name is available in applications when such names must be unique; the user submits the data, and the client-side validation is performed. As part of this process, an Ajax request is made to the server to validate the user name that has been requested. If the user name has been taken, a validation error is displayed so that the user can enter another value.