FTP proxy problem in C# application

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C#

private void Upload(string filename)
        {
            string ftpHost = ftpServerIP;
            //here correct hostname or IP of the ftp server to be given  
            FileInfo fileInf = new FileInfo(filename);
            string ftpFullPath = "ftp://" + ftpHost + fileInf.Name;
            MessageBox.Show(ftpFullPath);
            FtpWebRequest ftp = (FtpWebRequest)FtpWebRequest.Create(ftpFullPath);
            ftp.Credentials = new NetworkCredential(ftpUserID, ftpPassword);
            //userid and password for the ftp server to given  
            ftp.KeepAlive = true;
            ftp.UseBinary = true;
            ftp.Method = WebRequestMethods.Ftp.UploadFile;
            FileStream fs = File.OpenRead(filename);
            byte[] buffer = new byte[fs.Length];
            fs.Read(buffer, 0, buffer.Length);
            fs.Close();
            Stream ftpStream = ftp.GetRequestStream();
            ftpStream.Write(buffer, 0, buffer.Length);
}

[edit]Added pre tag[/ediit]

When I assign proxy it gives the exception
ftp.Proxy = new System.Net.WebProxy("http://10.16.5.39:3128/", true);
"The requested FTP command is not supported when using HTTP proxy."
When I set ftp.Proxy = null; it gives the exception
"Unable to connect to the remote server"
Help me to solve the issue.