title: Linq-to-Entities Include method not found
body: <p>I am using EF4 within a MVC3 application and I was looking for a way to view all my contacts within a given workgroup. In the controller I specified:</p>
  
  <pre><code>var wg = from w in _repo.Workgroups.Include("Contact").ToList();
  </code></pre>
  
  <p>but I get the following error:</p>
  
  <blockquote>
    <p>'System.Linq.IQueryable' does not contain a definition for 'Include' and no extension method 'Include' accepting a first argument of type 'System.Linq.IQueryable' could be found (are you missing a using directive or an assembly reference?)</p>
  </blockquote>
  
  <p>I though this method was built into EF4. Do I have enable it somehow?</p>