var client = new MongoClient( new MongoClientSettings { 
                                                ConnectionMode = ConnectionMode.Direct, 
                                                Server = new MongoServerAddress("x.x.x.x", 27017), 
                                         });
var database = client.GetDatabase("db");            
var collection = database.GetCollection<BsonDocument>("collection");
var document = collection.Find(new BsonDocument()).FirstOrDefault();