title: Fetch inherited instances from MongoDB using C#
body: <p>I'm using the official MongoDb C# driver.  </p>
  
  <p>My scenario: I store objects into MongoDb. All objects are instances of classes that inherit from the same root class. 
  At design time I do not know all classes that can be stored (i.e they can be plugged in) - so I need some way to tell the serializer/driver how to map the classes to documents (descriminators in the document). </p>
  
  <p>Anyone got any ideas?</p>