C# 上传文件至FTP_c# 使用fluentftp上传文件报错

private void Ftp(string file_name)
{
  
        FileInfo fi = new FileInfo("D:\\\\" + file_name + ".csv");
        //定义上传目录
        string url = "ftp://transfer.ymtc.com/Data_Transfer/" + file_name + ".csv";
 
        FtpWebRequest ftp;
        ftp = (FtpWebRequest)FtpWebRequest.Create(new Uri(url));
        //ftp账号密码
        ftp.Credentials = new NetworkCredential("账号", "密码");
        //公司都是代理上网，所以如果不加这句话，就会报错误【使用 HTTP 代理时不支持请求的 FTP 命令。】
        ftp.Proxy = null;
        ftp.KeepAlive = false;
        ftp.Method = WebRequestMethods.Ftp.UploadFile;
        ftp.UseBinary = true;
        ftp.ContentLength = fi.Length;
 
        int buffLength = 2048;
        byte[] be = new byte[buffLength];
        int contentLen;
        using (FileStream fs = fi.OpenRead())
        {
            using (Stream s = ftp.GetRequestStream())
            {
                contentLen = fs.Read(be, 0, buffLength);
                while (contentLen != 0)
                {
                    s.Write(be, 0, contentLen);
                    contentLen = fs.Read(be, 0, buffLength);
                }
                s.Close();
            }
            fs.Close();
        }
}