title: projection wont work in mongodb c# driver
body: <p>I have class that executes mongo queries
  its works but when I send projection in query, projection won't work
  and mongo return hole document</p>
  
  <p>whats the matter?</p>
  
  <pre><code> query = new QueryDocument( BsonSerializer.Deserialize&lt;BsonDocument&gt;(queryStr));
  </code></pre>
  
  <p><code>queryStr="{family:'james'},{}" =&gt;</code> its ok</p>
  
  <p><code>queryStr="{},{family:0}" =&gt;</code> not ok. return all columns, but don't want to get family column</p>
  
  <p><strong>Remember:</strong> just want this method. not another methods. because want send any query to mongo. I've read mapped mongo objects like ORMs. </p>
  
  <p>just want this method. thanks</p>