how to rename the directory on the FTP server using FtpWebRequest(Careful:not to rename the file in the directory)

 i got an error at line 11  to rename the directory(its old name is "0",i want to change to "1")  when i ran the code as follow.

 anybody can help me ?

main code:

1             private function void ftpRename()
2    {
3                URI = @"ftp://"+Server ip+"/0";
4                System.Net.FtpWebRequest ftp = GetRequest(URI);
5                //Set request to delete
6                ftp.Method = System.Net.WebRequestMethods.Ftp.Rename;
7                ftp.RenameTo = "/1";
8                try
9                {
10                   //get response but ignore it
11                   string str = GetStringResponse(ftp);     ///error here!!!
12               }
13               catch (Exception)
14               {
15                   return false;
16               }
17   }
18    //Get the basic FtpWebRequest object with the
19           //common settings and security
20           private FtpWebRequest GetRequest(string URI)
21           {
22               URI = @"ftp://" + URI;
23              
24               FtpWebRequest result = (FtpWebRequest)FtpWebRequest.Create(URI);
25           
26               result.Credentials = GetCredentials();
27             
28               result.EnableSsl = false;
29            
30               result.KeepAlive = false;
31               // support for passive connections 
32               result.UsePassive = true;
33               return result;
34           }
35           
36           private string GetStringResponse(FtpWebRequest ftp)
37           {
38               //Get the result, streaming to a string
39               string result = "";
40               using (FtpWebResponse response = (FtpWebResponse)ftp.GetResponse())
41               {
42                   long size = response.ContentLength;
43                   using (Stream datastream = response.GetResponseStream())
44                   {
45                       using (StreamReader sr = new StreamReader(datastream, System.Text.Encoding.UTF8))
46                       {
47                           result = sr.ReadToEnd();
48                           sr.Close();
49                       }
50   
51                       datastream.Close();
52                   }
53   
54                   response.Close();
55               }
56   
57               return result;
58           }