title: ObjectSet library is not being found?
body: <pre><code>using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Text;
  using System.Data;
  using ModelLayer.PocoModels;
  using System.Data.Objects;
  
  namespace ModelLayer
  {
      public class NorthwindDataContext : ObjectContext
      {
          private ObjectSet&lt;Category&gt; _categories;
          private ObjectSet&lt;Product&gt; _products;
          public NorthwindDataContext()
              : base("name=NorthwindEntities",
                  "NorthwindEntities")
          {
              _categories = CreateObjectSet&lt;Category&gt;();
              _products = CreateObjectSet&lt;Product&gt;();
          }
      }
  }
  </code></pre>
  
  <p>In the above code I get an error as it cant find the <code>ObjectSet</code> class and gives me type or namespace not found error.While in the sample project it works fine it is under using <code>System.Data.Objects.ObjectSet</code> but I dont see that library in my current project?  I am using asp.net mvc and .net 4.0. Does anyone have any good ideas ?</p>