title: How to use an index with MongoCollection.Update()
body: <p>I am writing a method that updates a single document in a very large <code>MongoCollection</code>, 
  and I have an index that I want the <code>MongoCollection.Update()</code> call to use to drastically reduce lookup time, <br/>but I can't seem to find anything like <code>MongoCursor.SetHint(string indexName)</code>.  <br/></p>
  
  <p>Is using an index on an update operation possible?  <br/>If so, how?</p>