参考链接：https://www.cnblogs.com/taiyonghai/p/5604159.html
类：
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1 using System; 2 using System.Collections.Generic; 3 using System.IO; 4 using System.Linq; 5 using System.Net; 6 using System.Text; 7 using System.Windows.Forms; 8 using System.Threading.Tasks; 9 using System.Threading; 10 11 namespace httpTool 12 { 13 class HttpHelper 14 { 15 const int bytebuff = 1024; 16 const int ReadWriteTimeOut = 2 * 1000;//超时等待时间 17 const int TimeOutWait = 5 * 1000;//超时等待时间 18 const int MaxTryTime = 12; 19 20 private double totalSize, curReadSize, speed; 21 private int proc, remainTime; 22 private int totalTime = 0; 23 24 bool downLoadWorking = false; 25 26 string StrFileName = ""; 27 string StrUrl = ""; 28 29 string outMsg = ""; 30 31 public HttpHelper(string url, string savePath) 32 { 33 this.StrUrl = url; 34 this.StrFileName = savePath; 35 } 36 37 /// <summary> 38 /// 下载数据更新 39 /// </summary> 40 /// <param name="totalNum">下载文件总大小</param> 41 /// <param name="num">已下载文件大小</param> 42 /// <param name="proc">下载进度百分比</param> 43 /// <param name="speed">下载速度</param> 44 /// <param name="remainTime">剩余下载时间</param> 45 public delegate void delDownFileHandler(string totalNum, string num, int proc, string speed, string remainTime, string outMsg); 46 public delDownFileHandler processShow; 47 public delegate void delDownCompleted(); 48 public delDownCompleted processCompleted; 49 public System.Windows.Forms.Timer timer; 50 51 public void init() 52 { 53 timer.Interval = 100; 54 timer.Tick -= TickEventHandler; 55 timer.Tick += TickEventHandler; 56 timer.Enabled = true; 57 downLoadWorking = true; 58 } 59 60 /// <summary> 61 /// 获取文件大小 62 /// </summary> 63 /// <param name="size"></param> 64 /// <returns></returns> 65 private string GetSize(double size) 66 { 67 String[] units = new String[] { "B", "KB", "MB", "GB", "TB", "PB" }; 68 double mod = 1024.0; 69 int i = 0; 70 while (size >= mod) 71 { 72 size /= mod; 73 i++; 74 } 75 return Math.Round(size) + units[i]; 76 } 77 78 /// <summary> 79 /// 获取时间 80 /// </summary> 81 /// <param name="second"></param> 82 /// <returns></returns> 83 private string GetTime(int second) 84 { 85 return new DateTime(1970, 01, 01, 00, 00, 00).AddSeconds(second).ToString("HH:mm:ss"); 86 } 87 88 /// <summary> 89 /// 下载文件（同步） 支持断点续传 90 /// </summary> 91 public void DowLoadFile() 92 { 93 totalSize = GetFileContentLength(StrUrl); 94 95 //打开上次下载的文件或新建文件 96 long lStartPos = 0; 97 System.IO.FileStream fs; 98 if (System.IO.File.Exists(StrFileName)) 99 { 100 fs = System.IO.File.OpenWrite(StrFileName); 101 lStartPos = fs.Length; 102 fs.Seek(lStartPos, System.IO.SeekOrigin.Current); //移动文件流中的当前指针 103 } 104 else 105 { 106 fs = new System.IO.FileStream(StrFileName, System.IO.FileMode.Create); 107 lStartPos = 0; 108 } 109 110 curReadSize = lStartPos; 111 112 if (curReadSize == totalSize) 113 { 114 outMsg = "文件已下载！"; 115 processCompleted?.Invoke(); 116 timer.Enabled = false; 117 return; 118 } 119 120 //打开网络连接 121 try 122 { 123 System.Net.HttpWebRequest request = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create(StrUrl); 124 if (lStartPos > 0) 125 request.AddRange((int)lStartPos); //设置Range值 126 127 //向服务器请求，获得服务器回应数据流 128 System.IO.Stream ns = request.GetResponse().GetResponseStream(); 129 byte[] nbytes = new byte[bytebuff]; 130 int nReadSize = 0; 131 proc = 0; 132 133 do 134 { 135 136 nReadSize = ns.Read(nbytes, 0, bytebuff); 137 fs.Write(nbytes, 0, nReadSize); 138 139 //已下载大小 140 curReadSize += nReadSize; 141 //进度百分比 142 proc = (int)((curReadSize / totalSize) * 100); 143 //下载速度 144 speed = (curReadSize / totalTime) * 10; 145 //剩余时间 146 remainTime = (int)((totalSize / speed) - (totalTime / 10)); 147 148 if (downLoadWorking == false) 149 break; 150 151 } while (nReadSize > 0); 152 153 fs.Close(); 154 ns.Close(); 155 156 if (curReadSize == totalSize) 157 { 158 outMsg = "下载完成！"; 159 processCompleted?.Invoke(); 160 downLoadWorking = false; 161 } 162 } 163 catch (Exception ex) 164 { 165 fs.Close(); 166 outMsg = string.Format("下载失败：{0}", ex.ToString()); 167 } 168 } 169 170 public void DownLoadPause() 171 { 172 outMsg = "下载已暂停"; 173 downLoadWorking = false; 174 } 175 176 public void DownLoadContinue() 177 { 178 outMsg = "正在下载"; 179 downLoadWorking = true; 180 DownLoadStart(); 181 } 182 183 public void DownLoadStart() 184 { 185 Task.Run(() => 186 { 187 DowLoadFile(); 188 }); 189 } 190 191 192 /// <summary> 193 /// 定时器方法 194 /// </summary> 195 /// <param name="sender"></param> 196 /// <param name="e"></param> 197 private void TickEventHandler(object sender, EventArgs e) 198 { 199 processShow?.Invoke(GetSize(totalSize), 200 GetSize(curReadSize), 201 proc, 202 string.Format("{0}/s", GetSize(speed)), 203 GetTime(remainTime), 204 outMsg 205 ); 206 if (downLoadWorking == true) 207 { 208 totalTime++; 209 } 210 } 211 212 /// <summary> 213 /// 获取下载文件长度 214 /// </summary> 215 /// <param name="url"></param> 216 /// <returns></returns> 217 public long GetFileContentLength(string url) 218 { 219 HttpWebRequest request = null; 220 try 221 { 222 request = (HttpWebRequest)HttpWebRequest.Create(url); 223 //request.Timeout = TimeOutWait; 224 //request.ReadWriteTimeout = ReadWriteTimeOut; 225 //向服务器请求，获得服务器回应数据流 226 WebResponse respone = request.GetResponse(); 227 request.Abort(); 228 return respone.ContentLength; 229 } 230 catch (Exception e) 231 { 232 if (request != null) 233 request.Abort(); 234 return 0; 235 } 236 } 237 } 238 }
页面调用
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1 using System; 2 using System.Collections.Generic; 3 using System.ComponentModel; 4 using System.Data; 5 using System.Drawing; 6 using System.Linq; 7 using System.Text; 8 using System.Threading.Tasks; 9 using System.Windows.Forms; 10 using httpTool; 11 using System.Threading; 12 13 namespace DownLoadDemo1 14 { 15 public partial class Form1 : Form 16 { 17 static string url = "http://speedtest.dallas.linode.com/100MB-dallas.bin"; //下载地址 18 19 static string temp = System.Environment.GetEnvironmentVariable("TEMP"); 20 static string loadFilefolder = new System.IO.DirectoryInfo(temp).FullName + @"\" + "100MB-dallas.bin"; 21 22 Thread td; 23 HttpHelper httpManager = new HttpHelper(url, loadFilefolder); 24 25 public Form1() 26 { 27 InitializeComponent(); 28 } 29 30 private void Form1_Load(object sender, EventArgs e) 31 { 32 httpManager.timer = new System.Windows.Forms.Timer(); 33 httpManager.processShow += processSho; 34 httpManager.processCompleted += processComplete; 35 httpManager.init(); 36 37 } 38 39 public void processSho(string totalNum, string num, int proc, string speed, string remainTime, string msg) 40 { 41 this.label1.Text = string.Format("文件大小：{0}", totalNum); 42 this.label2.Text = string.Format("已下载：{0}", num); 43 this.label3.Text = string.Format("进度：{0}%", proc); 44 this.label4.Text = msg; 45 this.label5.Text = string.Format("速度：{0}",speed); 46 this.label6.Text = string.Format("剩余时间：{0}",remainTime); 47 } 48 49 private void processComplete() 50 { 51 MessageBox.Show("文件下载完成！", "提示"); 52 } 53 54 private void button1_Click(object sender, EventArgs e) 55 { 56 httpManager.DownLoadStart(); 57 58 } 59 60 private void button2_Click(object sender, EventArgs e) 61 { 62 httpManager.DownLoadPause(); 63 } 64 65 private void button3_Click(object sender, EventArgs e) 66 { 67 httpManager.DownLoadContinue(); 68 } 69 } 70 }
效果
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