private void Download(string filePath, string fileName)
{
    FtpWebRequest reqFTP;

    try
    {
        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(ftpUserID, ftpPassword);

        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);
    }
}

------解决方案--------------------

完整一点
C# code

public class FtpFile
    {
        string ftpServerIP;

        public string FtpServerIP
        {
            get { return ftpServerIP; }
            set { ftpServerIP = value; }
        }
        string ftpUserID;

        public string FtpUserID
        {
            get { return ftpUserID; }
            set { ftpUserID = value; }
        }
        string ftpPassword;

        public string FtpPassword
        {
            get { return ftpPassword; }
            set { ftpPassword = value; }
        }
        FtpWebRequest reqFTP;
        public static string FtpServer = System.Configuration.ConfigurationSettings.AppSettings["FtpServer"];
        public static string FtpUser = System.Configuration.ConfigurationSettings.AppSettings["FtpUser"];
        public static string FtpPwd = System.Configuration.ConfigurationSettings.AppSettings["FtpPwd"];
        private void Connect(String path)//连接ftp
        {
            // 根据uri创建FtpWebRequest对象
            reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri(path));
            // 指定数据传输类型
            reqFTP.UseBinary = true;
            // ftp用户名和密码
            reqFTP.Credentials = new NetworkCredential(ftpUserID, ftpPassword);
        }
        public FtpFile(string ftpServerIP, string ftpUserID, string ftpPassword)
        {
            this.ftpServerIP = ftpServerIP;
            this.ftpUserID = ftpUserID;
            this.ftpPassword = ftpPassword;
        }
        public FtpFile()
        {
            this.ftpServerIP = FtpServer;
            this.ftpUserID = FtpUser;
            this.ftpPassword = FtpPwd;
        }

------解决方案--------------------
C# code

  //都调用这个
        private string[] GetFileList(string path, string WRMethods)//上面的代码示例了如何从ftp服务器上获得文件列表
        {
            string[] downloadFiles;
            StringBuilder result = new StringBuilder();
            try
            {
                Connect(path);
                reqFTP.Method = WRMethods;
                WebResponse response = reqFTP.GetResponse();
                StreamReader reader = new StreamReader(response.GetResponseStream(), System.Text.Encoding.UTF8);//中文文件名
                string line = reader.ReadLine();
                while (line != null)
                {
                    result.Append(line);
                    result.Append