怎样判断FTP上的文件夹是否存在，如果存在就下载到本地电脑上，怎么实现呢?

Question

C#怎样判断FTP上的文件夹是否存在，如果存在就下载到本地电脑上，怎么实现呢?  跪求详解

Answer 1

通过Socket发送FTP指令来进行FTP目录操作
http://www.google.com.hk/search?hl=zh-CN&source=hp&q=ftp+%E5%91%BD%E4%BB%A4&meta=&aq=1&aqi=g10&aql=&oq=ftp&gs_rfai=
http://www.google.com.hk/search?hl=zh-CN&newwindow=1&safe=strict&q=ftp+%E5%91%BD%E4%BB%A4+c%23+socket&meta=&aq=f&aqi=&aql=&oq=&gs_rfai=

Answer 2

这样！        /// <summary>
        /// 获取FTP服务器文件信息
        /// </summary>
        /// <param name="allFiles">打包成string的文件信息，每个文件一行</param>
        /// <returns>获取文件是否成功</returns>
        private bool getFtpFileInfo(out string allFiles)
        {
            bool retResult = false;
            allFiles = "";            ftpClientInstance = new ftpOperater();
            fileInfos = ftpClientInstance.GetFileList();            StringBuilder sbFileInfo = new StringBuilder();
            if (fileInfos != null)
            {
                foreach (string afile in fileInfos)
                {
                    sbFileInfo.Append(afile);
                    sbFileInfo.Append("\n");
                }
                allFiles += "获取FTP服务器文件信息成功！\n";
                allFiles += sbFileInfo.ToString();
                retResult = true;
            }
            else
            {
                allFiles += "获取FTP上PCM数据文件信息失败！";
                retResult = false;
            }
            return retResult;
        }ftpOperater类的定义如下：    /// <summary>
    /// 封装了FTP的两个操作：下载文件Download()和获取FTP服务器上文件列表信息GetFileList()
    /// </summary>
    public class ftpOperater
    {
        private string ftpServerIP;
        private string ftpUser;
        private string ftpPwd;        private SystemParaReader spReader;        public ftpOperater()
        {
            spReader = new SystemParaReader();
            this.ftpServerIP = spReader.GetSysParaValue("ftpServer");
            this.ftpUser = spReader.GetSysParaValue("ftpUser");
            this.ftpPwd = spReader.GetSysParaValue("ftpPwd");
        }        /// <summary>
        /// 获取ftp服务器上的文件信息
        /// </summary>
        /// <returns>存储了所有文件信息的字符串数组</returns>
        public string[] GetFileList()
        {
            string[] downloadFiles;
            StringBuilder result = new StringBuilder();
            FtpWebRequest reqFTP;
            try
            {
                reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri("ftp://" + ftpServerIP + "/"));
                reqFTP.UseBinary = true;
                reqFTP.Credentials = new NetworkCredential(ftpUser, ftpPwd);
                reqFTP.Method = WebRequestMethods.Ftp.ListDirectory;
                WebResponse response = reqFTP.GetResponse();
                StreamReader reader = new StreamReader(response.GetResponseStream());                string line = reader.ReadLine();
                while (line != null)
                {
                    result.Append(line);
                    result.Append("\n");
                    line = reader.ReadLine();
                }
                result.Remove(result.ToString().LastIndexOf('\n'), 1);
                reader.Close();
                response.Close();                return result.ToString().Split('\n');
            }
            catch (Exception ex)
            {
                System.Windows.Forms.MessageBox.Show("获取文件信息失败:"+ex.Message,"操作失败",MessageBoxButtons.OK,MessageBoxIcon.Error);
                downloadFiles = null;
                return downloadFiles;
            }
        }        /// <summary>
        /// 获取FTP上指定文件的大小
        /// </summary>
        /// <param name="filename">文件名</param>
        /// <returns>文件大小</returns>
        public long GetFileSize(string filename)
        {
            FtpWebRequest reqFTP;
            long fileSize = 0;
            try
            {
                reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri("ftp://" + ftpServerIP + "/" + filename));
                reqFTP.Method = WebRequestMethods.Ftp.GetFileSize;
                reqFTP.UseBinary = true;
                reqFTP.Credentials = new NetworkCredential(ftpUser, ftpPwd);
                FtpWebResponse response = (FtpWebResponse)reqFTP.GetResponse();
                Stream ftpStream = response.GetResponseStream();
                fileSize = response.ContentLength;                ftpStream.Close();
                response.Close();
            }
            catch (Exception ex)
            {
                MessageBox.Show("获取文件大小时，出现异常:\n" + ex.Message, "获取文件大小失败！", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
            return fileSize;
        }        /// <summary>
        /// 实现ftp下载操作
        /// </summary>
        /// <param name="filePath">保存到本地的文件名</param>
        /// <param name="fileName">远程文件名</param>
        public void Download(string filePath, string fileName)
        {
            FtpWebRequest reqFTP;
            try
            {
                //filePath = <<The full path where the file is to be created.>>, 
                //fileName = <<Name of the file to be created(Need not be the name of the file on FTP server).>>
                FileStream outputStream = new FileStream(filePath + "\\" + fileName, FileMode.Create);                reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri("ftp://" + ftpServerIP + "/" + fileName));
                reqFTP.Method = WebRequestMethods.Ftp.DownloadFile;
                reqFTP.UseBinary = true;
                reqFTP.Credentials = new NetworkCredential(ftpUser, ftpPwd);
                FtpWebResponse response = (FtpWebResponse)reqFTP.GetResponse();
                Stream ftpStream = response.GetResponseStream();
                long cl = response.ContentLength;
                int bufferSize = 2048;
                int readCount;
                byte[] buffer = new byte[bufferSize];                readCount = ftpStream.Read(buffer, 0, bufferSize);
                while (readCount > 0)
                {
                    outputStream.Write(buffer, 0, readCount);
                    readCount = ftpStream.Read(buffer, 0, bufferSize);
                }                ftpStream.Close();
                outputStream.Close();
                response.Close();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }
    }