title: MVC Validation: Service Layer or Data Annotations
body: <p>I hope this isn't terribly subjective, but when it comes to validating business logic, I see two paths that, unless I'm mistaken, deliver pretty much the same result:</p>
  
  <ul>
  <li><p>Use a service layer where all validation on your models is performed (ref: <a href="http://www.asp.net/mvc/tutorials/older-versions/models-%28data%29/validating-with-a-service-layer-cs" rel="nofollow">http://www.asp.net/mvc/tutorials/older-versions/models-%28data%29/validating-with-a-service-layer-cs</a>)</p></li>
  <li><p>Decorate your models with Data Annotations</p></li>
  </ul>
  
  <p>In the first instance, the model is a dumb container for data, and in the second, the model knows about its valid state. Above and beyond that, is there nuance between the two that I'm missing? Should one be used over the other in some instances?</p>
  
  <p>Thanks,</p>
  
  <p>Chris</p>