title: Silverlight + Web Application with WCF missing system.linq
body: <p>I'm creating a little Silverlight LOB app. I created the app + web in Blend 4 and I've opened the solution in VS2010 to add the WCF service. When I do so, it shows an error on <code>using System.Linq;</code>. It says:</p>
  
  <blockquote>
    <p>The type or namespace name 'Linq' does not exist in the namespace 'System'(are you missing an assembly reference?)</p>
  </blockquote>
  
  <p>I had VS2010 create the WCF service and I've tried to re-add the reference in for .NET 4 System.Core.dll.</p>
  
  <p>So newbie dev question... What did I do wrong :)</p>