HOW TO: Perform Credit Card Validation in ASP.NET

Credit Card Validator control for ASP.NET by Paul Ingles (CodeProject) - outlines how to create a credit card validator control fully derived from BaseValidator.
Using the Luhn algorithm to validate credit cards by Jason Young (YTechie Blog) - shows how to create an ASP.NET validator to validate credit cards using the Luhn algorithm.
Credit Card Validation with LINQ by Mike Hadlow - illustrates a LINQ-based mod 10 validation algorithm implementation; example is written as an extension method validator.