Conect to Network System in C#.net

        try
            {
                string uri = "ftp://"  + ftpaddress + "/" + fileInf.Name;
                FtpWebRequest reqFTP;
                reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri(uri));
                reqFTP.Credentials = new NetworkCredential(username, password);
                reqFTP.KeepAlive = false;
                reqFTP.Method = WebRequestMethods.Ftp.GetFileSize;
                FtpWebResponse fb = (FtpWebResponse)reqFTP.GetResponse();
                long cnlen = fb.ContentLength;
                if (cnlen > 0)
                    MessageBox.Show("File is found");
            }
            catch(WebException ex)
            {
                // if(fw.StatusCode == FtpStatusCode.FileActionAborted)                             
                //if(es.Status == FtpStatusCode.ActionNotTakenFileUnavailable)
                FtpWebResponse fw = (FtpWebResponse)ex.Response;
                if (fw.StatusCode == FtpStatusCode.ActionNotTakenFileUnavailable)
                    MessageBox.Show("File Not Found");
            }           
        }