Insira um novo documento usando InsertOneAsync (.NET Driver 2.0)

 public async void Insert()
    {
         var client = new MongoClient("mongodb://localhost:27017");
        var database = client.GetDatabase("foo");
        var collection = database.GetCollection<BsonDocument>("bar");

        var document = new BsonDocument { { "_id", 1 }, { "x", 2 } };
        await collection.InsertOneAsync(document);

    }