title: Ambigous reference using ColumnAttribute
body: <p>In one project, I was able to use ColumnAttribute without problems.</p>
  
  <p>In another, not. I have the following class in a test project:</p>
  
  <pre><code>class TestClass_x
  {
    [Key, Column(Order = 0)]
    public int i { get; set; }
  
    [Key, Column(Order = 1)]
    public string i2 { get; set; }
  
    public string str { get; set; }
  }
  </code></pre>
  
  <p>resulting in</p>
  
  <pre><code>Ambigous reference:
   System.ComponentModel.DataAnnotations.Schema.ColumnAttribute
   System.ComponentModel.DataAnnotations.Schema.ColumnAttribute
  match
  </code></pre>
  
  <p>I have the following references added to the test project:</p>
  
  <ul>
  <li>EntityFramework (v 4.4.0.0) </li>
  <li>Project to test</li>
  <li>Another project to test</li>
  <li>A third project to test</li>
  <li>Microsoft.VisualStudio.Quality.Tools.UnitTestFramework (v 10.0.0.0)</li>
  <li>PresentationFramework (v 4.0.0.0)</li>
  <li>System (v 4.0.0.0)</li>
  <li>System.ComponentModel.DataAnnotations (v 4.0.0.0)</li>
  </ul>