Amazon S3 helper

gistfile1.txt

public class AmazonS3Helper
    {
        private readonly string _amazonAccessKey;
        private readonly string _amazonSecretKey;
        private const string BucketName = "zertisedpm";

        public AmazonS3Helper(string amazonAccessKey, string amazonSecretKey )
        {
            _amazonAccessKey = amazonAccessKey;
            _amazonSecretKey = amazonSecretKey;
        }

        public string GenerateFilename(string originalFileName)
        {
            return ObjectId.GenerateNewId().ToString() + Path.GetExtension(originalFileName);
        }

        public void UploadFile(string fileName, Stream inputStream)
        {
            using (var client = Amazon.AWSClientFactory.CreateAmazonS3Client(_amazonAccessKey, _amazonSecretKey))
            {
                var request = new PutObjectRequest()
                    .WithBucketName(BucketName)
                    .WithCannedACL(S3CannedACL.Private)
                    .WithKey("docs/" + fileName);

                request.InputStream = inputStream;

                client.PutObject(request);
            }
        }

        public byte[] DownloadFile(string fileName)
        {
            byte[] fileBytes;

            using (var client = Amazon.AWSClientFactory.CreateAmazonS3Client(_amazonAccessKey, _amazonSecretKey))
            {
                var request = new GetObjectRequest()
                    .WithBucketName(BucketName)
                    .WithKey("docs/" + fileName);

                using (var response = client.GetObject(request))
                {
                    var numBytesRead = 0;
                    var numBytesToRead = (int)response.ContentLength;
                    fileBytes = new byte[numBytesToRead];

                    using (var stream = new MemoryStream())
                    {
                        while (numBytesToRead > 0)
                        {
                            var n = response.ResponseStream.Read(fileBytes, numBytesRead, numBytesToRead);
                            stream.Write(fileBytes, numBytesRead, n);

                            if (n == 0) break;
                            numBytesRead += n;
                            numBytesToRead -= n;
                        }
                    }
                }
            }

            return fileBytes;
        }

        public void DeleteFile(string fileName)
        {
            using (var client = Amazon.AWSClientFactory.CreateAmazonS3Client(_amazonAccessKey, _amazonSecretKey))
            {
                var request = new DeleteObjectRequest()
                    .WithBucketName(BucketName)
                    .WithKey("docs/" + fileName);

                client.DeleteObject(request);
            }
        }

        public IEnumerable<T> BuildUploadFilesResponse<T>(HttpFileCollectionBase files, Func<string, string, T> itemBuilder)
        {
            for (int i = 0; i < files.Count; i++)
            {
                var file = files[i];
                var filename = GenerateFilename(file.FileName);
                if (file.ContentLength > 0)
                {
                    UploadFile(filename, file.InputStream);
                }
                yield return itemBuilder(filename, file.FileName);
            }
        }
    }