C# 多线程下载

下面是一个完整的多线程下载源码，我在写代码的时候遇到点问题也放在下面，希望大家别犯相同的错误。

问题1、线程偷懒？
在程序中我设置N个线程去下载时，然而有的线程却偷懒去了，当时非常奇怪，花了很多时间在代码上。
这其实是因为服务器不支持多线程下载造成的，大部分专业的下载站都禁止多线程下载，既然是服务器的原因那就没法了，在这里我想提一下在IIS7中启用和禁止多线程的方法。
应用程序池?-》?右击属性“高级设置”?-》?进程模型?-》?最大工作进程数(这里便是设置允许多少线程)
至于IIS6也在应用程序池里设置，应用程序池-?》右击属性?-》?性能?-》?最大工作进程数。好了废话不说了，看下面的源码：

使用：

using System.Net;using System.IO;using System.Collections.Generic;using System.Threading;using System;public class JhxzThreading{    private int _threadNum;             //线程数量    private long _fileSize;             //文件大小    private string _extName;            //文件扩展名    private string _fileUrl;            //文件地址    private string _fileName;           //文件名    private string _savePath;           //保存路径    private short _threadCompleteNum;   //线程完成数量    private bool _isComplete;           //是否完成    private volatile int _downloadSize; //当前下载大小    private Thread[] _thread;           //线程数组    private List<string> _tempFiles = new List<string>();    public string FileName    {        get        {            return _fileName;        }        set        {            _fileName = value;        }    }    public long FileSize    {        get        {            return _fileSize;        }    }    public int DownloadSize    {        get        {            return _downloadSize;        }    }    public bool IsComplete    {        get        {            return _isComplete;        }        set        {            _isComplete = value;        }    }    public int ThreadNum    {        get        {            return _threadNum;        }        set        {            _threadNum = value;        }    }    public string SavePath    {        get        {            return _savePath;        }        set        {            _savePath = value;        }    }    public JhxzThreading(int threahNum, string fileUrl, string savePath)    {        this._threadNum = threahNum;        this._thread = new Thread[threahNum];        this._fileUrl = fileUrl;        this._savePath = savePath;    }    public void Start()    {        HttpWebRequest request = (HttpWebRequest) WebRequest.Create(_fileUrl);        HttpWebResponse response = (HttpWebResponse) request.GetResponse();        _extName = response.ResponseUri.ToString().Substring(response.ResponseUri.ToString().LastIndexOf('.'));//获取真实扩展名        _fileSize = response.ContentLength;        int singelNum = (int) (_fileSize / _threadNum);      //平均分配        int remainder = (int) (_fileSize % _threadNum);      //获取剩余的        request.Abort();        response.Close();        for (int i = 0; i < _threadNum; i++)        {            List<int> range = new List<int>();            range.Add(i * singelNum);            if (remainder != 0 && (_threadNum - 1) == i)    //剩余的交给最后一个线程                range.Add(i * singelNum + singelNum + remainder - 1);            else                range.Add(i * singelNum + singelNum - 1);            _thread[i] = new Thread(() => { Download(range[0], range[1]); });            _thread[i].Name = "jhxz_{0}".Formart(i + 1);            _thread[i].Start();        }    }    private void Download(int from, int to)    {        Stream httpFileStream = null, localFileStram = null;        try        {            string tmpFileBlock = @"{0}\{1}_{2}.dat".Formart(_savePath, _fileName, Thread.CurrentThread.Name);            _tempFiles.Add(tmpFileBlock);            HttpWebRequest httprequest = (HttpWebRequest) WebRequest.Create(_fileUrl);            httprequest.AddRange(from, to);            HttpWebResponse httpresponse = (HttpWebResponse) httprequest.GetResponse();            httpFileStream = httpresponse.GetResponseStream();            localFileStram = new FileStream(tmpFileBlock, FileMode.Create);            byte[] by = new byte[5000];            int getByteSize = httpFileStream.Read(by, 0, (int) by.Length);           //Read方法将返回读入by变量中的总字节数            while (getByteSize > 0)            {                Thread.Sleep(20);                _downloadSize += getByteSize;                localFileStram.Write(by, 0, getByteSize);                getByteSize = httpFileStream.Read(by, 0, (int) by.Length);            }            _threadCompleteNum++;        }        catch (Exception ex)        {            throw new Exception(ex.Message.ToString());        }        finally        {            if (httpFileStream != null)                httpFileStream.Dispose();            if (localFileStram != null)                localFileStram.Dispose();        }        if (_threadCompleteNum == _threadNum)        {            _isComplete = true;            Complete();        }    }    private void Complete()    {        Stream mergeFile = new FileStream(@"{0}\{1}{2}".Formart(_savePath, _fileName, _extName), FileMode.Create);        BinaryWriter AddWriter = new BinaryWriter(mergeFile);        foreach (string file in _tempFiles)        {            using (FileStream fs = new FileStream(file, FileMode.Open))            {                BinaryReader TempReader = new BinaryReader(fs);                AddWriter.Write(TempReader.ReadBytes((int) fs.Length));                TempReader.Close();            }            File.Delete(file);        }        AddWriter.Close();    }}

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