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   源码介绍

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断点续传下载文件带进度条源码

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;//引入输入输出功能
using System.Net;//网络请求
using System.Text.RegularExpressions;//用于正则表达式字符串处理
using System.Runtime.InteropServices;//引入WinAPI功能函数
using System.Threading;//处理线程

namespace DownLoadFile
{
    public partial class MainFrm : Form
    {
        public MainFrm()
        {
            InitializeComponent();
        }

       static string FileName = "";//记录要下载的文件名
       static long FileLength = 0; //记录文件大小
       static long count = 0;
       static long sPosstion = 0;//本地已下载完的大小
        private void Form1_Load(object sender, EventArgs e)
       {
           try
           {
               //监视剪贴板是否有数据
               string strPath = Clipboard.GetData(DataFormats.Text).ToString();
               //验证网址格式
               if (Regex.IsMatch(strPath, @"http(s)?://([\w-] \.) [\w-] (/[\w- ./?%&=]*)?"))
               {
                   textBox1.Text = strPath;
                   FileName = strPath.Substring(strPath.LastIndexOf("/")   1);
               }
               textBox1.Text = ReadString("SysSet", "lasturl", "", Application.StartupPath   "\\SysSet.ini");
               //读取文件存放的默认路径
               textBox2.Text = ReadString("SysSet", "RootPath", "", Application.StartupPath   "\\SysSet.ini");
               textBox3.Text = ReadString("SysSet", "lastfile", "", Application.StartupPath   "\\SysSet.ini");
               FileLength = Convert.ToInt32(ReadString("SysSet", "totallength", "", Application.StartupPath   "\\SysSet.ini"));
               string file = ReadString("SysSet", "lastfile", "", Application.StartupPath   "\\SysSet.ini");
               FileStream s = new FileStream(file, FileMode.Open, FileAccess.Read);
               count = s.Length;
               s.Close();//这里记得关了
           }
           catch
           {
               MessageBox.Show("配置文件加载失败！");
           }
               
           
        }

        //下载文件
        private void button1_Click(object sender, EventArgs e)
        {
            ThreadPool.QueueUserWorkItem(new WaitCallback(delegate{
            if (textBox2.Text.EndsWith("\\"))
                DownloadFile(textBox2.Text   FileName, textBox1.Text);
            else
                DownloadFile(textBox2.Text   "\\"   FileName, textBox1.Text);
           
            })); 
     
        }

        //选择存放路径，并存储到INI文件中
        private void button4_Click(object sender, EventArgs e)
        {
            folderBrowserDialog1.SelectedPath = ReadString("SysSet", "RootPath", "", Application.StartupPath   "\\SysSet.ini");
            if (folderBrowserDialog1.ShowDialog() == DialogResult.OK)
            {
                textBox2.Text = folderBrowserDialog1.SelectedPath;
                WritePrivateProfileString("SysSet", "RootPath", textBox2.Text, Application.StartupPath   "\\SysSet.ini");
               
            }
           
        }

        //下载地址改变时，相应的下载文件发生改变
        private void textBox1_TextChanged(object sender, EventArgs e)
        {
            if (textBox1.Text.Contains("/"))
            {
                textBox3.Text = textBox1.Text.Substring(textBox1.Text.LastIndexOf("/")   1);
                FileName = textBox3.Text;
            }
        }

        #region 以断点续传方式下载文件
        /// <summary>
        /// 以断点续传方式下载文件
        /// </summary>
        /// <param name="strFileName">下载文件的保存路径</param>
        /// <param name="strUrl">文件下载地址</param>
        public void DownloadFile(string strFileName, string strUrl)
        {
            //打开上次下载的文件或新建文件
           int CompletedLength = 0;//记录已完成的大小
          
            FileStream FStream;
            if (File.Exists(strFileName))
            {
                FStream = File.OpenWrite(strFileName);
                sPosstion = FStream.Length;
                FStream.Seek(sPosstion, SeekOrigin.Current);//移动文件流中的当前指针
            }
            else
            {
                FStream = new FileStream(strFileName, FileMode.Create);
                sPosstion = 0;
            }
            //打开网络连接
            try
            {
                HttpWebRequest myRequest = (HttpWebRequest)HttpWebRequest.Create(strUrl);
                if (CompletedLength > 0)
                    myRequest.AddRange((int)CompletedLength);//设置Range值
                //向服务器请求，获得服务器的回应数据流
                HttpWebResponse webResponse = (HttpWebResponse)myRequest.GetResponse();
                FileLength = webResponse.ContentLength;//文件大小
                Stream myStream = webResponse.GetResponseStream();
                byte[] btContent = new byte[1024];
               if(count<=0) count  = sPosstion;

                while ((CompletedLength = myStream.Read(btContent, 0, 1024)) > 0)
                {
                    FStream.Write(btContent, 0, CompletedLength);
                    count  = CompletedLength;
                }
                FStream.Close();
                myStream.Close();
                MessageBox.Show("文件下载完成！", "提示", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
            catch
            {
                FStream.Close();
            }
        }
        #endregion

        #region 为INI文件中指定的节点取得字符串
        /// <summary>
        /// 为INI文件中指定的节点取得字符串
        /// </summary>
        /// <param name="lpAppName">欲在其中查找关键字的节点名称</param>
        /// <param name="lpKeyName">欲获取的项名</param>
        /// <param name="lpDefault">指定的项没有找到时返回的默认值</param>
        /// <param name="lpReturnedString">指定一个字串缓冲区，长度至少为nSize</param>
        /// <param name="nSize">指定装载到lpReturnedString缓冲区的最大字符数量</param>
        /// <param name="lpFileName">INI文件名</param>
        /// <returns>复制到lpReturnedString缓冲区的字节数量，其中不包括那些NULL中止字符</returns>
        [DllImport("kernel32")]
        public static extern int GetPrivateProfileString(
            string lpAppName,
            string lpKeyName,
            string lpDefault,
            StringBuilder lpReturnedString,
            int nSize,
            string lpFileName);
        #endregion

        #region 修改INI文件中内容
        /// <summary>
        /// 修改INI文件中内容
        /// </summary>
        /// <param name="lpApplicationName">欲在其中写入的节点名称</param>
        /// <param name="lpKeyName">欲设置的项名</param>
        /// <param name="lpString">要写入的新字符串</param>
        /// <param name="lpFileName">INI文件名</param>
        /// <returns>非零表示成功，零表示失败</returns>
        [DllImport("kernel32")]
        public static extern int WritePrivateProfileString(
            string lpApplicationName,
            string lpKeyName,
            string lpString,
            string lpFileName);
        #endregion

        #region 从INI文件中读取指定节点的内容
        /// <summary>
        /// 从INI文件中读取指定节点的内容
        /// </summary>
        /// <param name="section">INI节点</param>
        /// <param name="key">节点下的项</param>
        /// <param name="def">没有找到内容时返回的默认值</param>
        /// <param name="def">要读取的INI文件</param>
        /// <returns>读取的节点内容</returns>
        public static string ReadString(string section, string key, string def, string fileName)
        {
            StringBuilder temp = new StringBuilder(1024);
            GetPrivateProfileString(section, key, def, temp, 1024, fileName);
            return temp.ToString();
        }
        #endregion

        private void button3_Click(object sender, EventArgs e)
        {
            Save();
            this.Close();
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            this.progressBar1.Maximum = (int)FileLength;
            this.progressBar1.Value = (int)count;
            this.Text = string.Format("已完成{0}/{1}",count.ToString(),FileLength);
            Save();
        }

        private void MainFrm_FormClosing(object sender, FormClosingEventArgs e)
        {
            Save();
        }
        private void Save()
        {
            WritePrivateProfileString("SysSet", "lastfile", string.Format("{0}\\{1}", textBox2.Text.Trim(), FileName), Application.StartupPath   "\\SysSet.ini");
            WritePrivateProfileString("SysSet", "lasturl", textBox1.Text.Trim(), Application.StartupPath   "\\SysSet.ini");
            WritePrivateProfileString("SysSet", "totallength", FileLength.ToString(), Application.StartupPath   "\\SysSet.ini");
            Application.DoEvents();
        }
    }
}