ASP.NET 4 Unleashed

Creating Custom Validation Controls

In this final section, you learn how to create custom validation controls. We create two custom controls. First, we create a LengthValidator control that enables you to validate the length of an entry in a form field. Next, we create an AjaxValidator control. The AjaxValidator control performs validation on the client by passing information back to a custom function defined on the server.

You create a new validation control by deriving a new control from the BaseValidator class. As its name implies, the BaseValidator class is the base class for all the validation controls, including the RequiredFieldValidator and RegularExpressionValidator controls.

The BaseValidator class is a MustInherit (abstract) class, ...