public ActionResult Index([Bind(Include = "CardType, CreditCardNumber")] CreditCard card)
 {
     if (ModelState.IsValid)
     {
         // Amex
         if (card.CardType == 1)
         {
             card.Result = CardValidator.IsValidAmex(card.CreditCardNumber) ? "Valid" : "Invalid";
         }
         // Discover
         else if (card.CardType == 2)
         {
             card.Result = CardValidator.IsValidDiscover(card.CreditCardNumber) ? "Valid" : "Invalid";
         }
         // Mastercard
         else if (card.CardType == 3)
         {
             card.Result = CardValidator.IsValidMastercard(card.CreditCardNumber) ? "Valid" : "Invalid";
         }
         // Visa
         else
         {
             card.Result = CardValidator.IsValidVisa(card.CreditCardNumber) ? "Valid" : "Invalid";
         }
     }
     return(View(card));
 }