C#限速下载网络文件的方法实例

C#限速下载网络文件的方法，具体如下：

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Net;
using System.Text;
using System.Text.Regularexpressions;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;
using Common.Utils;
using Utils;

namespace 爬虫
{
  public partial class Form1 : Form
  {
    #region 变量
    /// 

    /// 已完成字节数
    /// 
    private long completedCount = 0;
    /// 

    /// 是否完成
    /// 
    private bool isCompleted = true;
    /// 

    /// 数据块队列
    /// 
    private ConcurrentQueue msQueue = new ConcurrentQueue();
    /// 

    /// 下载开始位置
    /// 
    private long range = 0;
    /// 

    /// 文件大小
    /// 
    private long total = 0;
    /// 

    /// 一段时间内的完成节点数，计算网速用
    /// 
    private long unitCount = 0;
    /// 

    /// 上次计时时间，计算网速用
    /// 
    private DateTime lastTime = DateTime.MinValue;
    /// 

    /// 一段时间内的完成字节数，控制网速用
    /// 
    private long unitCountForLimit = 0;
    /// 

    /// 上次计时时间，控制网速用
    /// 
    private DateTime lastTimeForLimit = DateTime.MinValue;
    /// 

    /// 下载文件sleep时间，控制速度用
    /// 
    private int sleepTime = 1;
    #endregion

    #region Form1
    public Form1()
    {
      InitializeComponent();
    }
    #endregion

    #region Form1_Load
    private void Form1_Load(object sender, EventArgs e)
    {
      lblMsg.Text = string.Empty;
      lblByteMsg.Text = string.Empty;
      lblSpeed.Text = string.Empty;
    }
    #endregion

    #region Form1_FormClosing
    private void Form1_FormClosing(object sender, FormClosingEventArgs e)
    {

    }
    #endregion

    #region btnDownload_Click 下载
    private void btnDownload_Click(object sender, EventArgs e)
    {
      isCompleted = false;
      btnDownload.Enabled = false;
      string url = txtUrl.Text.Trim();
      string filePath = CreateFilePath(url);

      #region 下载线程
      Thread thread = new Thread(new ThreadStart(() =>
      {
 int tryTimes = 0;
 while (!HttpDownloadFile(url, filePath))
 {
   Thread.Sleep(10000);

   tryTimes++;
   LogUtil.Log("请求服务器失败，重新请求" + tryTimes.ToString() + "次");
   this.Invoke(new InvokeDelegate(() =>
   {
     lblMsg.Text = "请求服务器失败，重新请求" + tryTimes.ToString() + "次";
   }));
   HttpDownloadFile(url, filePath);
 }
      }));
      thread.IsBackground = true;
      thread.Start();
      #endregion

      #region 保存文件线程
      thread = new Thread(new ThreadStart(() =>
      {
 while (!isCompleted)
 {
   MemoryStream ms;
   if (msQueue.TryDequeue(out ms))
   {
     using (FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.Write))
     {
fs.Seek(completedCount, SeekOrigin.Begin);
fs.Write(ms.ToArray(), 0, (int)ms.Length);
fs.Close();
     }
     completedCount += ms.Length;
   }

   if (total != 0 && total == completedCount)
   {
     Thread.Sleep(100);
     isCompleted = true;
   }

   Thread.Sleep(1);
 }
      }));
      thread.IsBackground = true;
      thread.Start();
      #endregion

      #region 计算网速/进度线程
      thread = new Thread(new ThreadStart(() =>
      {
 while (!isCompleted)
 {
   Thread.Sleep(1000);

   if (lastTime != DateTime.MinValue)
   {
     double sec = DateTime.Now.Subtract(lastTime).TotalSeconds;
     double speed = unitCount / sec / 1024;

     try
     {
#region 显示速度
if (speed < 1024)
{
  this.Invoke(new InvokeDelegate(() =>
  {
    lblSpeed.Text = string.Format("{0}KB/S", speed.ToString("0.00"));
  }));
}
else
{
  this.Invoke(new InvokeDelegate(() =>
  {
    lblSpeed.Text = string.Format("{0}MB/S", (speed / 1024).ToString("0.00"));
  }));
}
#endregion

#region 显示进度
this.Invoke(new InvokeDelegate(() =>
{
  string strTotal = (total / 1024 / 1024).ToString("0.00") + "MB";
  if (total < 1024 * 1024)
  {
    strTotal = (total / 1024).ToString("0.00") + "KB";
  }
  string completed = (completedCount / 1024 / 1024).ToString("0.00") + "MB";
  if (completedCount < 1024 * 1024)
  {
    completed = (completedCount / 1024).ToString("0.00") + "KB";
  }
  lblMsg.Text = string.Format("进度：{0}/{1}", completed, strTotal);
  lblByteMsg.Text = string.Format("已下载：{0}rn总大小：{1}", completedCount, total);

  if (completedCount == total)
  {
    MessageBox.Show("完成");
  }
}));
#endregion
     }
     catch { }

     lastTime = DateTime.Now;
     unitCount = 0;
   }
 }
      }));
      thread.IsBackground = true;
      thread.Start();
      #endregion

      #region 限制网速线程
      thread = new Thread(new ThreadStart(() =>
      {
 while (!isCompleted)
 {
   Thread.Sleep(100);

   if (lastTimeForLimit != DateTime.MinValue)
   {
     double sec = DateTime.Now.Subtract(lastTimeForLimit).TotalSeconds;
     double speed = unitCountForLimit / sec / 1024;

     try
     {
#region 限速/解除限速
double limitSpeed = 0;
if (double.TryParse(txtSpeed.Text.Trim(), out limitSpeed))
{
  if (speed > limitSpeed && sleepTime < 1000)
  {
    sleepTime += 1;
  }
  if (speed < limitSpeed - 10 && sleepTime >= 2)
  {
    sleepTime -= 1;
  }
}
else
{
  this.Invoke(new InvokeDelegate(() =>
  {
    txtSpeed.Text = "100";
  }));
}
#endregion
     }
     catch { }

     lastTimeForLimit = DateTime.Now;
     unitCountForLimit = 0;
   }
 }
      }));
      thread.IsBackground = true;
      thread.Start();
      #endregion

    }
    #endregion

    #region HttpDownloadFile 下载文件
    /// 

    /// Http下载文件
    /// 
    public bool HttpDownloadFile(string url, string filePath)
    {
      try
      {
 if (!File.Exists(filePath))
 {
   using (FileStream fs = new FileStream(filePath, FileMode.Create))
   {
     fs.Close();
   }
 }
 else
 {
   FileInfo fileInfo = new FileInfo(filePath);
   range = fileInfo.Length;
 }

 // 设置参数
 HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
 request.UserAgent = "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.0; Trident/4.0)";
 request.Proxy = null;
 //发送请求并获取相应回应数据
 HttpWebResponse response = request.GetResponse() as HttpWebResponse;
 if (response.ContentLength == range)
 {
   this.Invoke(new InvokeDelegate(() =>
   {
     lblMsg.Text = "文件已下载";
   }));
   return true;
 }

 // 设置参数
 request = WebRequest.Create(url) as HttpWebRequest;
 request.UserAgent = "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.0; Trident/4.0)";
 request.Proxy = null;
 request.AddRange(range);
 //发送请求并获取相应回应数据
 response = request.GetResponse() as HttpWebResponse;
 //直到request.GetResponse()程序才开始向目标网页发送Post请求
 Stream responseStream = response.GetResponseStream();

 total = range + response.ContentLength;
 completedCount = range;

 MemoryStream ms = new MemoryStream();
 byte[] bArr = new byte[1024];
 lastTime = DateTime.Now;
 lastTimeForLimit = DateTime.Now;
 int size = responseStream.Read(bArr, 0, (int)bArr.Length);
 unitCount += size;
 unitCountForLimit += size;
 ms.Write(bArr, 0, size);
 while (!isCompleted)
 {
   size = responseStream.Read(bArr, 0, (int)bArr.Length);
   unitCount += size;
   unitCountForLimit += size;
   ms.Write(bArr, 0, size);
   if (ms.Length > 102400)
   {
     msQueue.Enqueue(ms);
     ms = new MemoryStream();
   }
   if (completedCount + ms.Length == total)
   {
     msQueue.Enqueue(ms);
     ms = new MemoryStream();
   }

   Thread.Sleep(sleepTime);
 }
 responseStream.Close();
 return true;
      }
      catch (Exception ex)
      {
 LogUtil.LogError(ex.Message + "rn" + ex.StackTrace);
 return false;
      }
    }
    #endregion

    #region 根据URL生成文件保存路径
    private string CreateFilePath(string url)
    {
      string path = Application.StartupPath + "\download";
      if (!Directory.Exists(path))
      {
 Directory.CreateDirectory(path);
      }

      string fileName = Path.GetFileName(url);
      if (fileName.IndexOf("?") > 0)
      {
 return path + "\" + fileName.Substring(0, fileName.IndexOf("?"));
      }
      else
      {
 return path + "\" + fileName;
      }
    }
    #endregion

  } //end Form1类
}

测试截图：

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