Utility helper for uploading large files to AWS S3 bucket

UploadUtilityHelper.cs

    public class UploadUtilityHelper
    {
        private readonly string bucketName = ConfigurationManager.AppSettings["BucketName"];
        private static readonly RegionEndpoint bucketRegion = RegionEndpoint.USEast1;
 
        public string UploadChunk(string fileName, string uploadId, int chunkIndex, int chunkMax, Stream stream, string prevETags)
        {
            var response = "";

            try
            {
                // Retreiving Previous ETags
                var eTags = new List<PartETag>();
                if (!string.IsNullOrEmpty(prevETags))
                {
                    eTags = SetAllETags(prevETags);
                }
                var _s3Client = new AmazonS3Client(ConfigurationManager.AppSettings["AWSAccessKey"],
                    ConfigurationManager.AppSettings["AWSSecretKey"], bucketRegion);

                var lastPart = ((chunkMax - chunkIndex) == 1) ? true : false;
                var partNumber = chunkIndex + 1;

                var ms = new MemoryStream();
                stream.CopyTo(ms);
                ms.Position = 0;

                //Step 1: build and send a multi upload request
                if (chunkIndex == 0)
                {
                    var initiateRequest = new InitiateMultipartUploadRequest
                    {
                        BucketName = bucketName,
                        Key = fileName
                    };

                    var initResponse = _s3Client.InitiateMultipartUpload(initiateRequest);
                    uploadId = initResponse.UploadId;
                }

                //Step 2: upload each chunk (this is run for every chunk unlike the other steps which are run once)
                var uploadRequest = new UploadPartRequest
                {
                    BucketName = bucketName,
                    Key = fileName,
                    UploadId = uploadId,
                    PartNumber = partNumber,
                    InputStream = ms,
                    IsLastPart = lastPart,
                    PartSize = ms.Length
                };

                var uploadResponse = _s3Client.UploadPart(uploadRequest);


                //Step 3: build and send the multipart complete request
                if (lastPart)
                {
                    eTags.Add(new PartETag
                    {
                        PartNumber = partNumber,
                        ETag = uploadResponse.ETag
                    });

                    var completeRequest = new CompleteMultipartUploadRequest
                    {
                        BucketName = bucketName,
                        Key = fileName,
                        UploadId = uploadId,
                        PartETags = eTags
                    };

                    var result = _s3Client.CompleteMultipartUpload(completeRequest);
                    //Set the uploadId and fileURLs with the response.
                    response = uploadRequest.UploadId + "|success|" + result.Location + "|";
                    //For image get thumbnail url
                    if (HasImageExtension(fileName.ToLower()))
                    {
                        //Send the Thumbnail URL
                        response += result.Location.Replace(uploadRequest.Key, "thumbnail/" + uploadRequest.Key);
                    } else
                    {
                        response += "";
                    }
                }
                else
                {
                    eTags.Add(new PartETag
                    {
                        PartNumber = partNumber,
                        ETag = uploadResponse.ETag
                    });

                    //Set the uploadId and eTags with the response
                    response = uploadRequest.UploadId + "|" + GetAllETags(eTags);
                }
            }
            catch (Exception e)
            {
                return null;
            }

            return response;
        }

        private List<PartETag> SetAllETags(string prevETags)
        {
            var partETags = new List<PartETag>();
            var splittedPrevETags = prevETags.Split(',');

            for (int i = 0; i < splittedPrevETags.Length; i++)
            {
                partETags.Add(new PartETag
                {
                    PartNumber = Int32.Parse(splittedPrevETags[i]),
                    ETag = splittedPrevETags[i + 1]
                });

                i = i + 1;
            }

            return partETags;
        }

        private string GetAllETags(List<PartETag> newETags)
        {
            var newPartETags = "";
            var isNotFirstTag = false;

            foreach (var eTag in newETags)
            {
                newPartETags += ((isNotFirstTag) ? "," : "") + (eTag.PartNumber.ToString() + ',' + eTag.ETag);
                isNotFirstTag = true;
            }

            return newPartETags;
        }

        private bool HasImageExtension(string fileName)
        {
            return (fileName.EndsWith(".png") || fileName.EndsWith(".jpg") || fileName.EndsWith(".jpeg") || fileName.EndsWith(".bmp")
                || fileName.EndsWith(".gif") || fileName.EndsWith(".tif") || fileName.EndsWith(".tiff"));
        }
    }

Do you have the driver code?