The following snippet implements a business rule that returns true if a given form element value is a valid credit card number formation and returns false if it is not. This method does not confirm existance or status. Specify the form's name in formName and the element's name in elementName.
This is a codebehind method and requires nothing in the xhtml markup.

The following snippet demonstrates suggested code for typical validation summary applications. The variable msg is a previously instantiated string that holds the accumulating list of validation errors to be displayed. This example assumes element "text1" on form "demo" is to be validated.
This is a codebehind method and requires nothing in the xhtml markup.

The following snippet demonstrates suggested code for adjacent error message applications. This example assumes element "text1" of form "demo" is to be validated with the results posted to an ajacent span tag "error1". (example: <span id="error1"></span>). This validator will fire every time the watched control loses focus.
This is a codebehind method and requires nothing in the xhtml markup other than the target element.

Test/Demonstration