C# 实现最简单的FTP下载功能

using System;
using System.Collections.Generic;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;
using System.Net;


namespace FTP_test2
{
    public partial class Form1 : Form
    {
        FtpWebRequest request;
        FtpWebResponse response;
        string fileName = "";
        StreamReader reader;

        public Form1()
        {
            InitializeComponent();
        }

        //连接按钮
        private void btn_connect_Click(object sender, EventArgs e)
        {
            //先清空列表框
            listBox1.Items.Clear();
            //对FTP的操作，使用FtpWebRequest类和FtpWebResponse类
            request = (FtpWebRequest)WebRequest.Create("ftp://192.168.0.98");
            request.Method = WebRequestMethods.Ftp.ListDirectory;
            request.Credentials = new NetworkCredential("user", "user");
            response = (FtpWebResponse)request.GetResponse();
            //再使用一个StreamReader类
            reader = new StreamReader(response.GetResponseStream());
            string filelist = reader.ReadToEnd();
            string[] list = filelist.Split(new char[]{'\r','\n'},StringSplitOptions.RemoveEmptyEntries);
            foreach(string i in list)
            {
                listBox1.Items.Add(i);
            }
            reader.Close();
            response.Close();
        }


        //下载按钮
        private void btn_down_Click(object sender, EventArgs e)
        {
            if (listBox1.SelectedItem == null)
            {
                MessageBox.Show("please chose a file!");
                return;
            }
            fileName = (string)listBox1.SelectedItem.ToString();
            string url = "D://Client//" + fileName;
            if(File.Exists(url))
            {
                if (MessageBox.Show("The location is already exit the" + fileName + ",Click OK will be covered!", "tooltip", 
                    MessageBoxButtons.OKCancel, MessageBoxIcon.Question) == DialogResult.Cancel)
                {
                    return;
                }
            }
            request = (FtpWebRequest)WebRequest.Create("ftp://192.168.0.98/" + fileName);
            request.Method = WebRequestMethods.Ftp.DownloadFile;
            request.Credentials = new NetworkCredential("user", "user");
            response = (FtpWebResponse)request.GetResponse();
            Stream responseStream = response.GetResponseStream();
            reader = new StreamReader(responseStream);
            StreamWriter writer = new StreamWriter(url);
            writer.Write(reader.ReadToEnd());
            writer.Close();
            reader.Close();
            MessageBox.Show(fileName + "download completed!");
        }
    }
}