.net core sftp

 using Renci.SshNet;

/// <summary>
        /// 上传文件到ftp服务器上
        /// </summary>
        /// <param name="file">文件</param>
        /// <param name="dateStr">文件时间戳</param>
        /// <returns>bool</returns>
        public static bool UploadFile(IFormFile file, long dateStr)
        {
            bool result = false;
            using (var client = new SftpClient(ftpAddress, 22, ftpUser, ftpPwd)) //创建连接对象，ftpAddress是ip地址如： 47.100.11.12  第二个参数是端口号，第三四个是用户名密码
            {
                client.Connect(); //连接

                MemoryStream fs = new MemoryStream();
                file.CopyTo(fs);

                client.BufferSize = 4 * 1024 * 1024;
                fs.Seek(0, SeekOrigin.Begin);

                client.UploadFile(fs, "/DirkWang/" + dateStr.ToString() + "_" + file.FileName);
                fs.Dispose();
                result = true;
            }

            return result;
        }

/// <summary>
        /// 下载附件
        /// </summary>
        /// <param name="fileName">附件名</param>
        /// <returns>byte[]</returns>
        public static byte[] DownloadFile(string fileName)
        {
            byte[] buffer = new byte[2 * 1024 * 1024];
            using (var client = new SftpClient(ftpAddress, 22, ftpUser, ftpPwd)) //创建连接对象
            {
                client.Connect(); //连接

                buffer = client.ReadAllBytes("/" + fileName);
            }

            return buffer;
        }