title: Multiple fields validation using Remote Validation
body: <p>I have the following model:</p>
  
  <pre><code>public class Customer
  {
      public string FirstName {get;set;}
  
      public string LastName {get; set;}
  
      [Remote("CardExisting", "Validation", AdditionalFields="FirstName,LastName")
      public string CardNumber {get; set;}
  }
  </code></pre>
  
  <p>CardExisting action will check that there is an existing record for the combination of cardNumber for the firstName and LastName.</p>
  
  <p>What if user will first enter the card number and then his name, I cant validate him, so when he returns and input his name I need to remote validate again, how can I do that when focus was already lost from cardnumber property? </p>