title: What linq reference am I missing?
body: <p>I'm in .NET Framework 4.0, have imports System.Linq and System.Data.Linq at the top. I'm querying an object of type <code>DataTable</code>. Plus I have System.Data.Linq, System.Xml.Linq, and System.Data as references.</p>
  
  <p>Why am I still getting
  <code>Expression of type 'System.Data.DataTable' is not queryable. Make sure you are not missing an assembly reference and/or namespace import for the LINQ provider</code>?</p>
  
  <p>My LINQ query:</p>
  
  <pre><code>dim count = (from row in changes select row.field(of String)("UnitID") distinct).count()
  </code></pre>