FtpManager类

public class FtpManager
    {
        /// <summary>
        /// 主机名
        /// </summary>
        string ftpServerIP;
        /// <summary>
        /// 登录名
        /// </summary>
        string ftpUserID;
        /// <summary>
        /// 登录密码
        /// </summary>
        string ftpPassword;

        FtpWebRequest ftpRequest;

        public FtpManager(string ftpServerIP, string ftpUserID, string ftpPassword)
        {
            this.ftpServerIP = ftpServerIP;

            this.ftpUserID = ftpUserID;

            this.ftpPassword = ftpPassword;
        }

        #region 连接ftp
        /// <summary>
        /// 连接ftp
        /// </summary>
        /// <param name="path"></param>
        public void Connect(String path)
        {

            // 根据uri创建FtpWebRequest对象
            ftpRequest = (FtpWebRequest)FtpWebRequest.Create(new Uri("ftp://" + ftpServerIP + "//" + path));
            //设置文件传输类型
            ftpRequest.UseBinary = true;
            //设置登录FTP帐号和密码
            ftpRequest.Credentials = new NetworkCredential(ftpUserID, ftpPassword);

        }        
        #endregion

        #region FTP获取文件列表

        /// <summary>
        /// FTP获取文件列表
        /// </summary>
        /// <param name="ftpServerIP"></param>
        /// <param name="ftpUserID"></param>
        /// <param name="ftpPassword"></param>
        /// <returns></returns>
        public string[] FTPGetFileList(string filePath)
        {
            //响应结果
            StringBuilder result = new StringBuilder();

            //FTP响应
            WebResponse ftpResponse = null;

            //FTP响应流
            StreamReader ftpResponsStream = null;

            try
            {
                Connect(filePath);

                ftpRequest.Method = WebRequestMethods.Ftp.ListDirectory;
                //生成FTP响应
                ftpResponse = ftpRequest.GetResponse();

                //FTP响应流
                ftpResponsStream = new StreamReader(ftpResponse.GetResponseStream());

                string line = ftpResponsStream.ReadLine();

                while (line != null)
                {
                    result.Append(line);
                    result.Append("\n");
                    line = ftpResponsStream.ReadLine();
                }

                //去掉结果列表中最后一个换行
                result.Remove(result.ToString().LastIndexOf('\n'), 1);

                //返回结果
                return result.ToString().Split('\n');
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
                return (null);
            }
            finally
            {
                if (ftpResponsStream != null)
                {
                    ftpResponsStream.Close();
                }

                if (ftpResponse != null)
                {
                    ftpResponse.Close();
                }
            }
        }

        #endregion

        #region FTP下载文件

        /// <summary>
        /// FTP下载文件
        /// </summary>
        /// <param name="ftpServerIP">FTP服务器IP</param>
        /// <param name="ftpUserID">FTP登录帐号</param>
        /// <param name="ftpPassword">FTP登录密码</param>
        /// <param name="saveFilePath">保存文件路径</param>
        /// <param name="saveFileName">保存文件名</param>
        /// <param name="downloadFileName">下载文件名</param>
        public void FTPDownloadFile(string path, string saveFileName, string downloadFileName)
        {
            //定义FTP响应对象
            FtpWebResponse ftpResponse = null;
            //存储流
            FileStream saveStream = null;
            //FTP数据流
            Stream ftpStream = null;

            try
            {
                Connect(downloadFileName);
                //生成下载文件
                saveStream = new FileStream(path + "\\" + saveFileName, FileMode.Create);

                //设置下载文件方法
                ftpRequest.Method = WebRequestMethods.Ftp.DownloadFile;

                //生成FTP响应对象
                ftpResponse = (FtpWebResponse)ftpRequest.GetResponse();

                //获取FTP响应流对象
                ftpStream = ftpResponse.GetResponseStream();

                //响应数据长度
                long cl = ftpResponse.ContentLength;

                int bufferSize = 2048;

                int readCount;

                byte[] buffer = new byte[bufferSize];

                //接收FTP文件流
                readCount = ftpStream.Read(buffer, 0, bufferSize);

                while (readCount > 0)
                {
                    saveStream.Write(buffer, 0, readCount);

                    readCount = ftpStream.Read(buffer, 0, bufferSize);
                }

            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
            finally
            {
                if (ftpStream != null)
                {
                    ftpStream.Close();
                }

                if (saveStream != null)
                {
                    saveStream.Close();
                }

                if (ftpResponse != null)
                {
                    ftpResponse.Close();
                }
            }
        }

        #endregion

        #region 从ftp服务器上获得文件列表
        /// <summary>
        /// 从ftp服务器上获得文件列表
        /// </summary>
        /// <param name="path"></param>
        /// <returns></returns>
        public string[] GetFileList(string path)
        {
            return FTPGetFileList(path);
        }       
        #endregion

        #region 文件存在检查
        /// <summary>
        /// 文件存在检查 
        /// </summary>
        /// <param name="fileName"></param>
        /// <returns></returns>
        public bool fileCheckExist(string fileName)
        {
            bool success = false;
            FtpWebResponse response = null;
            StreamReader reader = null;
            try
            {
                Connect(fileName);
                response = (FtpWebResponse)ftpRequest.GetResponse();
                reader = new StreamReader(response.GetResponseStream());
                string line = reader.ReadLine();
                if (line != null)
                {
                    success = true;
                }
            }
            catch (Exception)
            {
                success = false;
            }
            finally
            {
                if (reader != null)
                {
                    reader.Close();
                }

                if (response != null)
                {
                    response.Close();
                }
            }
            return success;
        }        
        #endregion

        #region 获取文件大小
        /// <summary>
        /// 获取文件大小
        /// </summary>
        /// <param name="filename"></param>
        /// <returns></returns>
        public long GetFileSize(string filepath)
        {
            long fileSize = 0;

            try
            {
                Connect(filepath);//连接      

                ftpRequest.Method = WebRequestMethods.Ftp.GetFileSize;

                FtpWebResponse response = (FtpWebResponse)ftpRequest.GetResponse();

                fileSize = response.ContentLength;

                response.Close();
            }

            catch (Exception ex)
            {
                throw ex;
            }

            return fileSize;

        }       
        #endregion
    }

调用方法：

FtpManager client = new FtpManager("192.168.1.101", "wangjun01", "qwer1234");
string parentUrl = "B";
client.FTPDownloadFile("D:", fileList[i], parentUrl);
//string[] fileList = client.FTPGetFileList(parentUrl);
//for (int i = 0; i < fileList.Length; i++)
//{
// client.FTPDownloadFile("D:", fileList[i], parentUrl);
//}