title: Description attribute on Enum giving error
body: <p>I am getting the following error from the description attribute as follows:</p>
  
  <blockquote>
    <p>Attribute 'Description' is not valid on this declaration type. It is
    only valid on 'method' declarations.</p>
  </blockquote>
  
  <pre><code>public enum TestEnum
  {
      [Description("Property 1")]
      Property1,
  }
  </code></pre>
  
  <p>I have never had this error before and Google isn't shedding much light. I guess it is a reference issue, but I'm not really sure.</p>