大家好，第一次发帖，请多关照。
文本对话已经实现了，我贴一下文件传输部分的代码。
这次真的是修了很多次代码但是不知道问题在哪里，希望能够请大家指点一下迷津。谢谢。

现在的问题是一传送文件就会出现错误，信息是：“System.ArgumentException”类型的异常在 mscorlib.dll 中发生，但未在用户代码中进行处理。
虽然他这么说了但是还是不太明白意思，所以求助一下大家。

这是发送文件时候的代码

if (fileInSending == false)
            {
                fileInSending = true;
                if (openFileDialog1.ShowDialog() == DialogResult.OK)
                {
                    FileInfo file = new FileInfo(openFileDialog1.FileName);
                    using (FileStream fs = new FileStream(openFileDialog1.FileName, FileMode.Open, FileAccess.Read))
                    {
                        BinaryWriter BWriter = new BinaryWriter(NetStream);
                        BWriter.Write(1);//代号1表示单个文件的总长度+文件名字节长度+文件名
                        BWriter.Write(fs.Length);//总长
                        byte[] nameBuffer = Encoding.UTF8.GetBytes(Path.GetFileName(file.FullName));
                        BWriter.Write(nameBuffer.Length);//文件名长度
                        NetStream.Write(nameBuffer, 0, nameBuffer.Length);//文件名
                        int len = 0;
                        byte[] buffer = new byte[4000];
                        while (NetStream.CanWrite)
                        {
                            len = fs.Read(buffer, 0, buffer.Length);
                            BWriter.Write(2);//代号2表示文件块的长度
                            BWriter.Write(len);
                            BWriter.Write(4);//代号4表示文件
                            NetStream.Write(buffer, 0, len);
                            buffer = new byte[4000];
                        }
                        fileInSending = false;
                    }
                }
            }

这是文件接收时的代码，里面用到的未申明变量都是类变量，backgroundWorker2组件是在计时器计时的时候触发的。因为把服务端和客户端都写在了一起，是通过界面上的一些选择来控制作为服务端还是客户端的，所以代码中有两个Client，Client是客户端，Subclient是服务端。命名好像确实有点奇怪了，请大家包涵。

        private void backgroundWorker2_DoWork(object sender, DoWorkEventArgs e)
        {
            if (Client is TcpClient)
            {
                if (Client.Available != 0)
                {
                    BinaryReader BReader = new BinaryReader(NetStream);
                    codeNum = BReader.ReadInt32();
                }
            }
            else if (Subclient is TcpClient)
            {
                if (Subclient.Available != 0)
                {
                    BinaryReader BReader = new BinaryReader(NetStream);
                    codeNum = BReader.ReadInt32();
                }
            }
        }

        private void backgroundWorker2_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            BinaryReader BReader = new BinaryReader(NetStream);
            #region 文本长度获取+文本读取
            if (codeNum == 0)//代号0表示文本长度
            {
                textLength = BReader.ReadInt32();
            }
            else if (codeNum == 3)//代号3表示文本
            {
                byte[] buffer = new byte[textLength];
                NetStream.Read(buffer, 0, buffer.Length);
                string text = "";
                text = Encoding.UTF8.GetString(buffer);
                textLength = 0;
                if (text != null)
                {
                    ShowMessage(text, false);
                }
            }
            #endregion
            #region 文件总长度获取+文件名获取+每个文件块大小获取+文件获取
            else if (codeNum == 1)//代号1表示单个文件的总长度+文件名字节长度+文件名
            {
                fileFullLength = BReader.ReadInt64();
                fileNameLength = BReader.ReadInt32();
                byte[] buffer = new byte[fileNameLength];
                fileName = Encoding.UTF8.GetString(buffer);
                fileRecievedLength = 0;
                FileDeliver fd = new FileDeliver();
                fd.fileRecievedPercent = (int)Math.Floor((double)(fileRecievedLength / fileFullLength)) * 100;
                if (saveFileDialog1.ShowDialog() == DialogResult.OK)
                {
                    saveFileDialog1.FileName = fileName;
                    fs = File.Create(saveFileDialog1.FileName);
                }
            }
            else if (codeNum == 2)
            {
                fileBlockLength = BReader.ReadInt32();
            }
            else if (codeNum == 4)
            {
                byte[] buffer = new byte[fileBlockLength];
                NetStream.Read(buffer, 0, buffer.Length);
                fs.Write(buffer, 0, buffer.Length);
                fileRecievedLength = fs.Length;
                //判定是否文件接收完毕
                if (fs.Length == fileFullLength)
                {
                    fileFullLength = 0;
                    fileNameLength = 0;
                    fileName = "";
                    fileBlockLength = 0;
                    fileRecievedLength = 0;
                }
            }
            #endregion
            
        }