C＃FTP：域名必填？ ，否则：远程服务器返回错误：（530）未登录

Question

您好我有以下代码：

ftpRequest = (FtpWebRequest)WebRequest.Create(host + remoteFile);
            /* Log in to the FTP Server with the User Name and Password Provided */
            if (withDomain)
            {
                ftpRequest.Credentials = new NetworkCredential(user.Normalize(), pass.Normalize(), dom.Normalize());
            }
            else
            {
                ftpRequest.Credentials = new NetworkCredential(user.Normalize(), pass.Normalize());
            }

            ftpRequest.UseBinary = true;
            ftpRequest.UsePassive = true;
            ftpRequest.KeepAlive = true;

            ftpRequest.Method = WebRequestMethods.Ftp.UploadFile;
            /* Establish Return Communication with the FTP Server */
            ftpStream = ftpRequest.GetRequestStream();

只有在未提供域名时才会出现错误，即如果只提供用户名和密码，我会收到错误消息。但是，相同的用户名和密码可以与Dreamweaver或其他FTP客户端工具一起使用。