protected override void RenderDataValidator( HtmlTextWriter writer )
{
base.RenderDataValidator( writer );
_regexValidator.ValidationExpression = @"\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*";
_regexValidator.ErrorMessage = "Email address is not valid";
_regexValidator.ValidationGroup = this.ValidationGroup;
_regexValidator.RenderControl( writer );
}