问为我的程序模拟FTP连接

EN

    private string LoadFTPFile()
    {
        string xml = null;
        string ftpAddress = "ftp://" + ftpLocation + "/" + PrintMachineParameters_BaseName + ".xml";
        try
        {

            logging.Write("Info", "LoadFTPFile()", "XML loaded from PLC: " + ftpAddress);

            WebClient request = new WebClient();
            request.Credentials = new NetworkCredential(ftpUserName, ftpPassword);
            byte[] fileData = request.DownloadData(ftpAddress);

            xml = System.Text.Encoding.Default.GetString(fileData);

            try
            {
                XmlDocument xmlDoc = new XmlDocument();
                xml = xml.Substring(xml.IndexOf("<"));
                xmlDoc.LoadXml(xml);
                XmlNode xmlNode = xmlDoc;
                xml = xmlNode.InnerXml;
            }
            catch (Exception exception)
            {
                string message = "Error loading FTP file: " + ftpAddress + Environment.NewLine;
                DisplayException("Error loading FTP file", message, exception);
                xml = null;
            }

        }
        catch (Exception exception)
        {
            string message = "Error loading FTP file: " + ftpAddress + Environment.NewLine;
            DisplayException("Error loading FTP file", message, exception);
            xml = null;
        }

        return xml;
    }