title: ASP.NET MVC: Custom Validation by DataAnnotation
body: <p>I have a Model with 4 properties which are of type string. I know you can validate the length of a single property by using the StringLength annotation. However I want to validate the length of the 4 properties combined. </p>
  
  <p>What is the MVC way to do this with data annotation?</p>
  
  <p>I'm asking this because I'm new to MVC and want to do it the correct way before making my own solution.</p>