title: Query filter ArgumentException when trying to extending OU principal
body: <p>I am try to create extension of principal for organizationalUnit using this code below</p>
  
  <pre><code>[DirectoryRdnPrefix("OU")]
  [DirectoryObjectClass("organizationalUnit")]
  public class OrganizationalUnitPrincipal : Principal
  {
      public OrganizationalUnitPrincipal(PrincipalContext Context_p)
      {
          PropertyInfo contextRaw = this.GetType().BaseType.GetProperty("ContextRaw",
              BindingFlags.Instance | BindingFlags.NonPublic);
          contextRaw.SetValue(this, Context_p, null);
      }
  }
  </code></pre>
  
  <p>But it throws the following error:</p>
  
  <pre><code>System.ArgumentException: Persisted Principal objects cannot be used as query filters.
  </code></pre>
  
  <p>This error occurs when I try retrieve organizationalUnit attributes and properties. </p>
  
  <p>Can this work or not?</p>
  
  <p>I want to achieve the same as show on this page <a href="http://msdn.microsoft.com/en-us/site/bb384372" rel="nofollow">http://msdn.microsoft.com/en-us/site/bb384372</a></p>