title: Cannot find using System.Data.Linq
body: <p>I'm using C#, EF 4 in asp.net 4 and VS 2010.</p>
  
  <p>I'm trying to load namespace <code>System.Data.Linq</code> with this code <code>using System.Data.Linq</code> 
  and I receive this error:</p>
  
  <blockquote>
    <p>Error 2   The type or namespace name 'Linq' does not exist in the namespace 'System.Data' (are you missing an assembly reference?)    </p>
  </blockquote>
  
  <p>Any idea what I'm doing wrong.</p>