public ResponseFile DownloadFile(RequestFile request)
        {
            ResponseFile result = new ResponseFile();

            FileStream stream = this.GetFileStream(Path.GetFullPath(request.FileName));
            stream.Seek(request.byteStart, SeekOrigin.Begin);
            result.FileName = request.FileName;
            result.Length = stream.Length;
            result.FileByteStream = stream;
            return result;
        }
        public void UploadFile(ResponseFile request)
        {
            string filePath = Path.GetFullPath(request.FileName);

            int chunkSize = 2048;
            byte[] buffer = new byte[chunkSize];

            using (FileStream stream = new FileStream(filePath, System.IO.FileMode.Append, System.IO.FileAccess.Write))
            {
                do
                {
                    int readbyte = request.FileByteStream.Read(buffer, 0, chunkSize);
                    if (readbyte == 0) break;

                    stream.Write(buffer, 0, readbyte);
                } while (true);
                stream.Close();
            }
        }