using (SftpClient client = new SftpClient(myConnectionInfo))
            {
                client.Connect();
                client.ChangeDirectory(destinationpath);
                using (FileStream fs = new FileStream(sourcefile, FileMode.Open))
                {
                        client.BufferSize = 4 * 1024;
                        client.UploadFile(fs, Path.GetFileName(sourcefile));
                }
                client.Disconnect();
            }

while ((currentBlockSize = source.Read