System.Net.Sockets.NetworkStream.CopyToAsync C# (CSharp) Method

        public override Task CopyToAsync(Stream destination, int bufferSize, CancellationToken cancellationToken)
        {
            // Validate arguments as would the base CopyToAsync
            StreamHelpers.ValidateCopyToArgs(this, destination, bufferSize);

            // And bail early if cancellation has already been requested
            if (cancellationToken.IsCancellationRequested)
            {
                return Task.FromCanceled(cancellationToken);
            }

            // Then do additional checks as ReadAsync would.

            if (_cleanedUp)
            {
                throw new ObjectDisposedException(this.GetType().FullName);
            }

            Socket streamSocket = _streamSocket;
            if (streamSocket == null)
            {
                throw new IOException(SR.Format(SR.net_io_readfailure, SR.net_io_connectionclosed));
            }

            // Do the copy.  We get a copy buffer from the shared pool, and we pass both it and the
            // socket into the copy as part of the event args so as to avoid additional fields in
            // the async method's state machine.
            return CopyToAsyncCore(
                destination,
                new AwaitableSocketAsyncEventArgs(streamSocket, ArrayPool<byte>.Shared.Rent(bufferSize)),
                cancellationToken);
        }

        /// <summary>
        /// Приём файла.
        /// </summary>
        /// <param name="socket">Сокет.</param>
        private void ReceiveFile(Socket socket)
        {
            // Генерируем уникальное имя для файла.
            var tmp_file_name = string.Format("{0}_{1}", DateTime.Now.Ticks, _fileCount);
            _fileCount++;

            var ns = new NetworkStream(socket);

            var remote_address = (socket.RemoteEndPoint as IPEndPoint).Address.ToString();
            var message_type = (MesasageType)ns.ReadByte();

            if (message_type == MesasageType.Text)
            {
                byte[] buffer = new byte[256];
                socket.Receive(buffer);
                Console.WriteLine("Принято сообщение: {0}", Encoding.Unicode.GetString(buffer));
                return;
            }

            var fs = new FileStream(tmp_file_name, FileMode.CreateNew);

            ns.CopyToAsync(fs).ContinueWith((ar) =>
            {
                fs.Close();
                fs.Dispose();
                ns.Close();
                ns.Dispose();
                FileInfo file = new FileInfo(tmp_file_name);
                if (FileSize.HasValue)
                {
                    if (FileSize == file.Length)
                    {
                        ReceviceFileCount++;
                    }
                    else
                    {
                        Console.WriteLine("Размер принятого файла не соответствует отправленному ({0} != {1}).", FileSize, file.Length);
                    }
                }

                Console.WriteLine("Получен файл");

                if (message_type == MesasageType.ReveiveFileAndExecProc)
                {
                    ExecProcAndSendFile(tmp_file_name, remote_address, _remotePort);
                }
                else
                {
                    if (IsDeleteFiles)
                    {
                        File.Delete(tmp_file_name);
                    }
                }
            });
        }