FTP(Refresh current directory) using C#

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C#3.5

Dear,
I have made a ftp file explorer but unfortunately it won't work when refresh current directory passive false mode not enter.

private void bgworkerImporter_DoWork(object sender, DoWorkEventArgs e)
{
    BackgroundWorker worker = sender as BackgroundWorker;
    for (; ; )
    {
        if (IsbusyImporter == false)
        {
            //working here
           // ftpSession.CurrentDirectory.Refresh();
            StartDownload();
        }
        if ((worker.CancellationPending == true))
        {
            e.Cancel = true;
            break;
        }
        else
        {
            // Perform a time consuming operation and report progress.
            System.Threading.Thread.Sleep(500);
        }
    }
}

then

public void StartDownload()
{
    //working here
    int files = ftpSession.CurrentDirectory.Files.Count();
    foreach (FtpFile file in ftpSession.CurrentDirectory.Files)
    {
      //  string Splitfile = file.Name.ToString();
      //  string[] Allsplitfile = Splitfile.Split('.');

        transferProgressBar.Value = 0;
        try
        {
            if (files >= 0)
            {
                // working here
                DownloadFile(file.Name.ToString());
                // Deletefile From FTP Directory
                if (IsSuccess == "Success")
                {
                    DeleteFTPFile(file.Name.ToString());
                }
            }
            else
            {
                IsbusyImporter = false;
            }


        }
        catch (Exception ex)
        {
            MessageBox.Show(IsDelete);
        }
    }
    IsbusyImporter = true;
   ftpSession.CurrentDirectory.Refresh();// here is problem refresh was not worked.

}

Refreshing current directory isn't work for why my listview kept previous deleted file and exception created.
Please tell what is the problem.I am trying a lot.if u don't understand then tell me how can i refresh current directory and get new ftp file in that directory
Mahmud
software Engineer