void Main()
{
  Console.WriteLine("lettura ftp");
  var list = ListDirectory(new Uri("ftp://ftp.kernel.org/pub/linux/kernel/v3.x/"));
  
  Console.WriteLine("\ntutti\n");
  foreach (var element in list)
  {
    Console.WriteLine(element);
  }
  
  Console.WriteLine("\nsolo quelli da cancellare\n");
  foreach (var element in list.Where (t => t.EndsWith(".gz", StringComparison.InvariantCultureIgnoreCase)))
  {
    Console.WriteLine(element);
    DeleteFileOnServer(new Uri(string.Format("ftp://ftp.kernel.org/pub/linux/kernel/v3.x/{0}", element)));
  }
}

// http://msdn.microsoft.com/en-us/library/ms229716(v=vs.110).aspx
public string[] ListDirectory(Uri serverUri)
{
    // The serverUri parameter should use the ftp:// scheme. 
    // It contains the name of the server file that is to be deleted. 
    // Example: ftp://contoso.com/someFile.txt. 
    //  

    if (serverUri.Scheme != Uri.UriSchemeFtp)
    {
        return new string[0];
    }
    // Get the object used to communicate with the server.
  FtpWebRequest request = (FtpWebRequest)WebRequest.Create(serverUri);
  request.Method = WebRequestMethods.Ftp.ListDirectory;
  
  // This example assumes the FTP site uses anonymous logon.
  request.Credentials = new NetworkCredential ("anonymous","janeDoe@contoso.com");
  
  FtpWebResponse response = (FtpWebResponse)request.GetResponse();
  
  Stream responseStream = response.GetResponseStream();
  StreamReader reader = new StreamReader(responseStream);
  
  var dirList = new List<string>();
  string line;
  while ((line = reader.ReadLine()) != null)
  {
    dirList.Add(line);
  }
  
  reader.Close();
  response.Close();
  
  return dirList.ToArray();
}

// http://msdn.microsoft.com/en-us/library/system.net.ftpwebrequest(v=vs.110).aspx
public bool DeleteFileOnServer(Uri serverUri)
{
    // The serverUri parameter should use the ftp:// scheme. 
    // It contains the name of the server file that is to be deleted. 
    // Example: ftp://contoso.com/someFile.txt. 
    //  

    if (serverUri.Scheme != Uri.UriSchemeFtp)
    {
        return false;
    }
    // Get the object used to communicate with the server.
    FtpWebRequest request = (FtpWebRequest)WebRequest.Create(serverUri);
    request.Method = WebRequestMethods.Ftp.DeleteFile;
  
  // This example assumes the FTP site uses anonymous logon.
  request.Credentials = new NetworkCredential ("anonymous","janeDoe@contoso.com");

    FtpWebResponse response = (FtpWebResponse) request.GetResponse();
    Console.WriteLine("Delete status: {0}",response.StatusDescription);  
    response.Close();
    return true;
}