public MongoDbContext(string connectionString, string defaultDatabase)
        {
            var helper = new MongoDbSettingsHelper(connectionString, defaultDatabase);

            _settings      = helper.client.Settings;
            _mongoDatabase = helper.client.GetDatabase(helper.DefaultDatabase);
        }
        public MongoDbContext()
        {
            var helper = new MongoDbSettingsHelper();

            _settings      = helper.client.Settings;
            _mongoDatabase = helper.client.GetDatabase(helper.DefaultDatabase);
            CreateCollection(helper.MongoCollections);
        }