title: How to do an upsert with MongoDB 2.0?
body: <p>The interface of MongoDB has completely changed from the previous one.
  <a href="http://mongodb.github.io/mongo-csharp-driver/2.0/getting_started/reading_and_writing/" rel="noreferrer">Here</a> you can see the official documentation with some examples about how to search, insert and update but what about upserts?</p>
  
  <p>Idea for meta:  I've tried to search on google and on SO but many resources refer to the old interface. Maybe it would be nice to create a MongoLegacy tag.</p>