SFTPHelper

 public class SFTPHelper
     {
         #region 字段或属性

         private readonly SftpClient _sftp;

         /// <summary>
         /// SFTP连接状态
         /// </summary>
         public bool Connected
         {
             get
             {
                 return _sftp.IsConnected;
             }
         }

         #endregion

         #region 构造函数

         /// <summary>
         /// 构造1
         /// </summary>
         /// <param name="ip">IP</param>
         /// <param name="port">端口</param>
         /// <param name="user">用户名</param>
         /// <param name="pwd">密码</param>
         public SFTPHelper(string ip, string port, string user, string pwd)
         {
             _sftp = new SftpClient(ip, Int32.Parse(port), user, pwd);
         }

         /// <summary>
         /// 构造2
         /// </summary>
         /// <param name="host">服务器地址</param>
         /// <param name="user">用户名</param>
         /// <param name="pwd">密码</param>
         public SFTPHelper(string host, string user, string pwd)
         {
             _sftp = new SftpClient(host, user, pwd);
         }

         #endregion

         #region 连接SFTP

         /// <summary>
         /// 连接SFTP
         /// </summary>
         /// <returns>true成功</returns>
         private void Connect()
         {
             if (!Connected)
             {
                 _sftp.Connect();
             }
         }

         #endregion

         #region 断开SFTP

         /// <summary>
         /// 断开SFTP
         /// </summary>
         private void Disconnect()
         {
             if (_sftp != null && Connected)
             {
                 _sftp.Disconnect();
             }
         }

         #endregion

         #region SFTP上传文件

         /// <summary>
         /// SFTP上传文件
         /// </summary>
         /// <param name="localPath">本地路径</param>
         /// <param name="remotePath">远程路径</param>
         public void UploadFile(string localPath, string remotePath)
         {
             using (var fileStream = File.OpenRead(localPath))
             {
                 Connect();
                 _sftp.UploadFile(fileStream, remotePath);
                 Disconnect();
             }
         }

         #endregion

         #region SFTP下载文件

         /// <summary>
         /// SFTP下载文件
         /// </summary>
         /// <param name="remotePath">远程路径</param>
         /// <param name="localPath">本地路径</param>
         public void DownloadFile(string remotePath, string localPath)
         {
             Connect();
             var byt = _sftp.ReadAllBytes(remotePath);
             Disconnect();
             File.WriteAllBytes(localPath, byt);
         }

         #endregion
     }