这两天在做一个项目，需要从ftp上拉取文件到本地进行数据读取，这里的文件主要是.xls、.xlsx、.csv文件(其他文件也可拉取，没有限制),下面分享一下我的思路及代码：

思路:主要分两步，第一步把ftp文件拉取到本地，未登陆时是无法拉取的，所以这里需要ftp地址、用户名、密码进行登陆操作，我写了个FtpHelper工具类用于拉取，第二步把本地文件进行读取这个就比较简单了。

FtpHelper工具类

   public class FtpHelper
    {
        //基本设置 
        private string ftpServer = @"ftp:XXXXXX";    //目标路径
        private string ftpDefaultUrl = "/XX/";    //ftp文件夹
        private string ftpUserName = "XX";   //ftp用户名
        private string ftpUserPwd = "XXX";   //ftp密码                                    
        private string downloadUrl = @"XXXXX";  //下载后的文件存放路径
        /// <summary>
        /// ftp拉取文件到本地
        /// </summary>
        public void FtpDownLoad()
        {
            //需要下载的文件名
            string fileName = "2021-01-11detail.csv";
            //需要现在的文件在ftp上的完整路径
            string fileUploadPath = ftpServer + ftpDefaultUrl;
            Uri uri = new Uri(fileUploadPath + "/" + fileName);
            //下载后存放的路径
            string FileName = Path.GetFullPath(downloadUrl) + Path.DirectorySeparatorChar.ToString() + Path.GetFileName(uri.LocalPath);
            //创建文件流
            FileStream fs = null;
            Stream responseStream = null;
            try
            {
                //判断ftp上是否存在此文件
                if (DirectoryIsExist(uri, ftpUserName, ftpUserPwd))
                {
                    //创建一个与FTP服务器联系的FtpWebRequest对象
                    FtpWebRequest request = (FtpWebRequest)WebRequest.Create(uri);
                    //设置请求的方法是FTP文件下载
                    request.Method = WebRequestMethods.Ftp.DownloadFile;
                    //连接登录FTP服务器
                    request.Credentials = new NetworkCredential(ftpUserName, ftpUserPwd);
                    //获取一个请求响应对象
                    FtpWebResponse response = (FtpWebResponse)request.GetResponse();
                    //获取请求的响应流
                    responseStream = response.GetResponseStream();
                    //判断本地文件是否存在，如果存在，则打开和重写本地文件
                    if (File.Exists(FileName))
                    {
                        fs = File.Open(FileName, FileMode.Open, FileAccess.ReadWrite);
                    }
                    else
                    {
                        fs = File.Create(FileName);
                    }

                    if (fs != null)
                    {
                        int buffer_count = 65536;
                        byte[] buffer = new byte[buffer_count];
                        int size = 0;
                        while ((size = responseStream.Read(buffer, 0, buffer_count)) > 0)
                        {
                            fs.Write(buffer, 0, size);
                        }
                        fs.Flush();
                        fs.Close();
                        responseStream.Close();
                    }
                } 
            }
            finally
            {
                if (fs != null)
                    fs.Close();
                if (responseStream != null)
                    responseStream.Close();
            }
        }

        /// <summary>
        /// 检测目录或文件是否存在
        /// </summary>
        /// <param name=”pFtpServerIP”></param>
        /// <param name=”pFtpUserID”></param>
        /// <param name=”pFtpPW”></param>
        /// <returns>false不存在，true存在</returns>
        public static bool DirectoryIsExist(Uri pFtpServerIP, string pFtpUserID, string pFtpPW)
        {
          string[] value = GetFileList(pFtpServerIP, pFtpUserID, pFtpPW);
            if (value == null)
            {
                return false;
            }
            else
            {
                return true;
            }
        }
        public static string[] GetFileList(Uri pFtpServerIP, string pFtpUserID, string pFtpPW)
        {
            StringBuilder result = new StringBuilder();
            try
            {
                FtpWebRequest reqFTP = (FtpWebRequest)FtpWebRequest.Create(pFtpServerIP);
                reqFTP.UseBinary = true;
                reqFTP.Credentials = new NetworkCredential(pFtpUserID, pFtpPW);
                reqFTP.Method = WebRequestMethods.Ftp.ListDirectoryDetails;
                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();
                }
                reader.Close();
                response.Close();
                return result.ToString().Split('\n');
            }
            catch
            {
                return null;
            }
        }
    }

文件读取：

         string filePath = (@"XXXXXXXXXXX");  //文件完整物理路径
            //判断文件是否存在
            if (!System.IO.File.Exists(filePath))
            {
                return SuccessResult("未轮询到今日文件");
            }
            DataTable dt = new DataTable();
            FileStream fs = new FileStream(filePath, System.IO.FileMode.Open, System.IO.FileAccess.Read);
            StreamReader sr = new StreamReader(fs, Encoding.Default);
            //记录每次读取的一行记录
            string strLine = "";
            //记录每行记录中的各字段内容
            string[] aryLine = null;
            string[] tableHead = null;
            //标示列数
            int columnCount = 0;
            //标示是否是读取的第一行
            bool IsFirst = true;
            //逐行读取CSV中的数据
            while ((strLine = sr.ReadLine()) != null)
            {
                if (IsFirst == true)
                {
                    tableHead = strLine.Split(',');
                    IsFirst = false;
                    columnCount = tableHead.Length;
                    //创建列
                    for (int i = 0; i < columnCount; i++)
                    {
                        DataColumn dc = new DataColumn(tableHead[i]);
                        dt.Columns.Add(dc);
                    }
                }
                else
                {
                    aryLine = strLine.Split(',');
                    DataRow dr = dt.NewRow();
                    for (int j = 0; j < columnCount; j++)
                    {
                        dr[j] = aryLine[j];
                    }
                    dt.Rows.Add(dr);
                }
            }
            if (aryLine != null && aryLine.Length > 0)
            {
                dt.DefaultView.Sort = tableHead[0] + " " + "asc";
            }
            sr.Close();
            fs.Close();
获取DataTable数据：
  dt.Rows[行号]["列名"].ToString();