cosmos change feed sql sdk

ChangeFeedSQLSDKProvider.cs

using Microsoft.Azure.Documents;
using Microsoft.Azure.Documents.Client;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace SQLSDK
{
    public class ChangeFeedSQLSDKProvider
    {
        private readonly DocumentClient _documentClient;

        private readonly Uri _collectionUri;

        public ChangeFeedSQLSDKProvider()
        {
        }
        public ChangeFeedSQLSDKProvider(string url, string key, string database, string collection)
        {
            _documentClient = new DocumentClient(new Uri(url), key,
                new ConnectionPolicy { ConnectionMode = ConnectionMode.Direct, ConnectionProtocol = Protocol.Tcp });

            _collectionUri = UriFactory.CreateDocumentCollectionUri(database, collection);


        }
        public async Task<int> GetChangeFeedAsync(string partitionName)
        {
            //var partionKeyRangeReponse = await _documentClient.ReadPartitionKeyRangeFeedAsync(_collectionUri, new FeedOptions
            //{
            //    RequestContinuation = await GetContinuationTokenForPartitionAsync(partitionName),
            //    PartitionKey = new PartitionKey(partitionName)
            //});

            //var partitionKeyRanges = new List<PartitionKeyRange>();
            //partitionKeyRanges.AddRange(partionKeyRangeReponse);

            var changeFeedQuery = _documentClient.CreateDocumentChangeFeedQuery(_collectionUri, new ChangeFeedOptions
            {
                StartFromBeginning = true,
                PartitionKey = new PartitionKey(partitionName),
                RequestContinuation = await GetContinuationTokenForPartitionAsync(partitionName),
            });

            var changeDocumentCount = 0;
            while (changeFeedQuery.HasMoreResults)
            {
                var response = await changeFeedQuery.ExecuteNextAsync<DeveloperModel>();
                foreach(var document in response)
                {
                    // TODO :: process changes here
                    Console.WriteLine($"changed for id - {document.Id} with name {document.Name} and skill {document.Skill}");
                }

                SetContinuationTokenForPartitionAsync(partitionName, response.ResponseContinuation);
                changeDocumentCount++;
            }

            return changeDocumentCount;
        }

        private async Task<string> GetContinuationTokenForPartitionAsync(string partitionName)
        {
            // TODO :: retrieve from a key value pair : persistence
            return null;
        }

        private async Task SetContinuationTokenForPartitionAsync(string partitionName, string lsn)
        {
            // TODO :: get the continuation token from persistence store
        }
    }
}