Retrieving /getting data from Mongo collection using C#

 public string GetSessionData(string transactionID)

        {

            try

            {

connectionString = ConfigurationManager.AppSettings[mongoConnKey];

                mongoDatabase = ConfigurationManager.AppSettings[mongodb];

                var client = new MongoClient(connectionString);

                var _database = client.GetDatabase(mongoDatabase);

                var collection = _database.GetCollection<BsonDocument>("TestCollection");          List<BsonDocument> result1 = _collection.AsQueryable<BsonDocument>().ToList();    

                return result1.ToString();      

}

catch (Exception ex)

            {

                return ex.ToString();

            }

}