The RegularExpressionValidator is a type of validation control that compares an input control against a pattern specified in the ValidationExpression. Regular expression validation is ideally suited for verifying predictable sequences of characters, such as those in social security numbers, email addresses, telephone numbers, and postal codes. Validation will succeed if the input control is empty, unless you also use a RequiredFieldValidator control. In this way, the RegularExpressionValidator control works identically to the System.Web.UI.WebControls.RegularExpressionValidator control for full-fledged web pages (although it won't render client-side validation code).
public class RegularExpressionValidator : BaseValidator { // Public Constructors public RegularExpressionValidator( ); // Public Instance Properties public string ValidationExpression{set; get; } // Protected Instance Methods protected override BaseValidator CreateWebValidator( ); // overrides BaseValidator protected override bool EvaluateIsValid( ); // overrides BaseValidator }