In FTPS server using C# code i can't able to list the full files

IN ftp server directory having nearly 4000 files but i can list 510 files only,(implicit over TLS security) can any help me to list the full files from dir....

here is my code

// try
                {
                    /* Create an FTP Request */
                    ftpRequest = (FtpWebRequest)FtpWebRequest.Create(host + "/" + directory);
                    /* Log in to the FTP Server with the User Name and Password Provided */
                    ftpRequest.Credentials = new NetworkCredential(user, pass);
                    /* When in doubt, use these options */
                    ftpRequest.UseBinary = true;
                    ftpRequest.UsePassive = true;
                    ftpRequest.KeepAlive = true;
                    ftpRequest.EnableSsl = true;
                //    X509Certificate x = new X509Certificate();
                    ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };
                    /* Specify the Type of FTP Request */
                    ftpRequest.Method = WebRequestMethods.Ftp.ListDirectory;
                    /* Establish Return Communication with the FTP Server */
                    ftpResponse = (FtpWebResponse)ftpRequest.GetResponse();
                    /* Establish Return Communication with the FTP Server */
                    ftpStream = ftpResponse.GetResponseStream();
                    /* Get the FTP Server's Response Stream */
                    StreamReader ftpReader = new StreamReader(ftpStream);
                    /* Store the Raw Response */
                    string directoryRaw = null;
                    /* Read Each Line of the Response and Append a Pipe to Each Line for Easy Parsing */
                    try { while (ftpReader.Peek() != -1) { directoryRaw += ftpReader.ReadLine() + "|"; } }
                    catch (Exception ex) { }
                    /* Resource Cleanup */
                    ftpReader.Close();
                    ftpStream.Close();
                    ftpResponse.Close();
                    ftpRequest = null;
                    /* Return the Directory Listing as a string Array by Parsing 'directoryRaw' with the Delimiter you Append (I use | in This Example) */
                    try { string[] directoryList = directoryRaw.Split("|".ToCharArray()); return directoryList; }
                    catch (Exception ex) { Console.WriteLine(ex.ToString()); }
                }
                catch (Exception ex)
                {
                    Console.WriteLine(ex.ToString());
                  
                   
                }
                //