本文是利用C# 实现FTP客户端的小例子，主要实现上传，下载，删除等功能，以供学习分享使用。

思路：

• 通过读取FTP站点的目录信息，列出对应的文件及文件夹。
• 双击目录，则显示子目录，如果是文件，则点击右键，进行下载和删除操作。
• 通过读取本地电脑的目录，以树状结构展示，选择本地文件，右键进行上传操作。
  

涉及知识点：

• FtpWebRequest【实现文件传输协议 (FTP) 客户端】 / FtpWebResponse【封装文件传输协议 (FTP) 服务器对请求的响应】Ftp的操作主要集中在两个类中。
• FlowLayoutPanel 【流布局面板】表示一个沿水平或垂直方向动态排放其内容的面板。
• ContextMenuStrip 【快捷菜单】 主要用于右键菜单。
• 资源文件：Resources 用于存放图片及其他资源。
  

效果图如下

左边：双击文件夹进入子目录，点击工具栏按钮‘上级目录'返回。文件点击右键进行操作。

右边：文件夹则点击前面+号展开。文件则点击右键进行上传。

核心代码如下

using System;using System.Collections.Generic;using System.IO;using System.Linq;using System.Net;using System.Text;using System.Threading;using System.Threading.Tasks;namespace FtpClient{ public class FtpHelper { #region 属性与构造函数 /// <summary> /// IP地址 /// </summary> public string IpAddr { get; set; } /// <summary> /// 相对路径 /// </summary> public string RelatePath { get; set; } /// <summary> /// 端口号 /// </summary> public string Port { get; set; } /// <summary> /// 用户名 /// </summary> public string UserName { get; set; } /// <summary> /// 密码 /// </summary> public string Password { get; set; } public FtpHelper() { } public FtpHelper(string ipAddr, string port, string userName, string password) { this.IpAddr = ipAddr; this.Port = port; this.UserName = userName; this.Password = password; } #endregion #region 方法 /// <summary> /// 下载文件 /// </summary> /// <param name="filePath"></param> /// <param name="isOk"></param> public void DownLoad(string filePath, out bool isOk) { string method = WebRequestMethods.Ftp.DownloadFile; var statusCode = FtpStatusCode.DataAlreadyOpen; FtpWebResponse response = callFtp(method); ReadByBytes(filePath, response, statusCode, out isOk); } public void UpLoad(string file,out bool isOk) { isOk = false; FileInfo fi = new FileInfo(file); FileStream fs = fi.OpenRead(); long length = fs.Length; string uri = string.Format("ftp://{0}:{1}{2}", this.IpAddr, this.Port, this.RelatePath); FtpWebRequest request = (FtpWebRequest)WebRequest.Create(uri); request.Credentials = new NetworkCredential(UserName, Password); request.Method = WebRequestMethods.Ftp.UploadFile; request.UseBinary = true; request.ContentLength = length; request.Timeout = 10 * 1000; try { Stream stream = request.GetRequestStream(); int BufferLength = 2048; //2K byte[] b = new byte[BufferLength]; int i; while ((i = fs.Read(b, 0, BufferLength)) > 0) { stream.Write(b, 0, i); } stream.Close(); stream.Dispose(); isOk = true; } catch (Exception ex) { Console.WriteLine(ex.ToString()); } finally { if (request != null) { request.Abort(); request = null; } } } /// <summary> /// 删除文件 /// </summary> /// <param name="isOk"></param> /// <returns></returns> public string[] DeleteFile(out bool isOk) { string method = WebRequestMethods.Ftp.DeleteFile; var statusCode = FtpStatusCode.FileActionOK; FtpWebResponse response = callFtp(method); return ReadByLine(response, statusCode, out isOk); } /// <summary> /// 展示目录 /// </summary> public string[] ListDirectory(out bool isOk) { string method = WebRequestMethods.Ftp.ListDirectoryDetails; var statusCode = FtpStatusCode.DataAlreadyOpen; FtpWebResponse response= callFtp(method); return ReadByLine(response, statusCode, out isOk); } /// <summary> /// 设置上级目录 /// </summary> public void SetPrePath() { string relatePath = this.RelatePath; if (string.IsNullOrEmpty(relatePath) || relatePath.LastIndexOf("/") == 0 ) { relatePath = ""; } else { relatePath = relatePath.Substring(0, relatePath.LastIndexOf("/")); } this.RelatePath = relatePath; } #endregion #region 私有方法 /// <summary> /// 调用Ftp,将命令发往Ftp并返回信息 /// </summary> /// <param name="method">要发往Ftp的命令</param> /// <returns></returns> private FtpWebResponse callFtp(string method) { string uri = string.Format("ftp://{0}:{1}{2}", this.IpAddr, this.Port, this.RelatePath); FtpWebRequest request; request = (FtpWebRequest)FtpWebRequest.Create(uri); request.UseBinary = true; request.UsePassive = true; request.Credentials = new NetworkCredential(UserName, Password); request.KeepAlive = false; request.Method = method; FtpWebResponse response = (FtpWebResponse)request.GetResponse(); return response; } /// <summary> /// 按行读取 /// </summary> /// <param name="response"></param> /// <param name="statusCode"></param> /// <param name="isOk"></param> /// <returns></returns> private string[] ReadByLine(FtpWebResponse response, FtpStatusCode statusCode,out bool isOk) { List<string> lstAccpet = new List<string>(); int i = 0; while (true) { if (response.StatusCode == statusCode) { using (StreamReader sr = new StreamReader(response.GetResponseStream())) { string line = sr.ReadLine(); while (!string.IsNullOrEmpty(line)) { lstAccpet.Add(line); line = sr.ReadLine(); } } isOk = true; break; } i++; if (i > 10) { isOk = false; break; } Thread.Sleep(200); } response.Close(); return lstAccpet.ToArray(); } private void ReadByBytes(string filePath,FtpWebResponse response, FtpStatusCode statusCode, out bool isOk) { isOk = false; int i = 0; while (true) { if (response.StatusCode == statusCode) { long length = response.ContentLength; int bufferSize = 2048; int readCount; byte[] buffer = new byte[bufferSize]; using (FileStream outputStream = new FileStream(filePath, FileMode.Create)) { using (Stream ftpStream = response.GetResponseStream()) { readCount = ftpStream.Read(buffer, 0, bufferSize); while (readCount > 0) { outputStream.Write(buffer, 0, readCount); readCount = ftpStream.Read(buffer, 0, bufferSize); } } } break; } i++; if (i > 10) { isOk = false; break; } Thread.Sleep(200); } response.Close(); } #endregion } /// <summary> /// Ftp内容类型枚举 /// </summary> public enum FtpContentType { undefined = 0, file = 1, folder = 2 }}

FTP服务端和客户端示意图

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