How to do an upsert with MongoDB 2.0?

Question

The interface of MongoDB has completely changed from the previous one. Here you can see the official documentation with some examples about how to search, insert and update

Answer 1

Pass an instance of UpdateOptions as the options parameter in UpdateOneAsync(filter, update, options), e.g.:

collection.UpdateOneAsync(p => p.Id == user.Id, 
    Builders<User>.Update.Set(p => p.Name, "John"), 
    new UpdateOptions { IsUpsert = true });

EDIT

To replace the document, call ReplaceOneAsync instead:

collection.ReplaceOneAsync(p => p.Id == user.Id, 
    user, 
    new ReplaceOptions { IsUpsert = true });