title: MongoDB Driver Query * Filter Definition Builder * Nin $nin Not in filter
body: <p>Has anyone used the C# .Net MongoDB Driver FilterDefinitionBuilder's not in filter? This is a simple example that I put together that I cannot seem to get to work. Assume that we must keep the collections as is. The goal is to retrieve only ArtistDetailsDocument's that are not in the specified ArtistGenresDocument list.</p>
  
  <p>The code will not compile and states "Cannot convert lambda expression to type 'MongoDB.Driver.FieldDefinition ArtistDetailsDocument,ArtistGenresDocument' because it is not a delegate type".  </p>
  
  <p>Appreciate the help! \m/ \m/</p>
  
  <pre><code>public class ArtistDetailsDocument
  {
      public ObjectId Id { get; set; }
      public String artist_ID { get; set; }
      public String artistName { get; set; }
  }
  
  public class ArtistGenresDocument
  {
      public ObjectId Id { get; set; }
      public String artist_ID { get; set; }
      public String genre { get; set; }
  }
  
  IEnumerable&lt;ArtistGenresDocument&gt; list = await ArtistGenresCollection.Find(x =&gt; x.genre == "Pop" | x.genre == "Easy Listening").ToListAsync();
  
  var filter = Builders&lt;ArtistDetailsDocument&gt;.Filter.Nin&lt;ArtistGenresDocument&gt;(x =&gt; x.artist_ID, list);
  
  var ArtistDetailsDocuments = ArtistDetailsCollection.Find(filter);
  </code></pre>