title: How can I get field's value without getting whole document?
body: <p>It seems to be really stupid question, I know. But anyway.</p>
  
  <p>Lats say, I have collection of documents of such structure:</p>
  
  <pre><code>{
    _id: idvalue, 
    name: namevalue, 
    location: 
    {
      long: longvalue, 
      lat: latvalue
    }
  }
  </code></pre>
  
  <p>And, of course, serialized class in C#.</p>
  
  <p>I need to get location of document specified by it's _id.</p>
  
  <p>I've tried to do this in following way:</p>
  
  <pre><code>var documentLocation = collection.FindOne("_id", new ObjectId(id)).Location;
  </code></pre>
  
  <p>But in this case the whole document will be taken from db. And I want to take only "location: {long: longvalue, lat: latvalue}" part of json.</p>
  
  <p>How can I do that?</p>