C#实现多线程下载文件的方法

本文实例讲述了C#实现多线程下载文件的方法。分享给大家供大家参考。具体实现方法如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Threading;
using System.Net;
namespace WfpApp
{
public class MultiDownload
{
 #region 变量
 private int _threadNum;    //线程数量
 private long _fileSize;    //文件大小
 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(实时的)
 private Thread[] _thread;   //线程数组
 private List<string> _tempFiles = new List<string>();
 private object locker = new object();
 #endregion
 #region 属性
 /// <summary>
 /// 文件名
 /// </summary>
 public string FileName
 {
  get
  {
   return _fileName;
  }
  set
  {
   _fileName = value;
  }
 }
 /// <summary>
 /// 文件大小
 /// </summary>
 public long FileSize
 {
  get
  {
   return _fileSize;
  }
 }
 /// <summary>
 /// 当前下载大小(实时的)
 /// </summary>
 public int DownloadSize
 {
  get
  {
   return _downloadSize;
  }
 }
 /// <summary>
 /// 是否完成
 /// </summary>
 public bool IsComplete
 {
  get
  {
   return _isComplete;
  }
 }
 /// <summary>
 /// 线程数量
 /// </summary>
 public int ThreadNum
 {
  get
  {
   return _threadNum;
  }
 }
 /// <summary>
 /// 保存路径
 /// </summary>
 public string SavePath
 {
  get
  {
   return _savePath;
  }
  set
  {
   _savePath = value;
  }
 }
 #endregion
 /// <summary>
 /// 构造函数
 /// </summary>
 /// <param name="threahNum">线程数量</param>
 /// <param name="fileUrl">文件Url路径</param>
 /// <param name="savePath">本地保存路径</param>
 public MultiDownload(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();
  _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);
   //下载指定位置的数据
   int[] ran = new int[] { range[0], range[1] };
   _thread[i] = new Thread(new ParameterizedThreadStart(Download));
   _thread[i].Name = System.IO.Path.GetFileNameWithoutExtension(_fileUrl) + "_{0}".Replace("{0}", Convert.ToString(i + 1));
   _thread[i].Start(ran);
  }
 }
 private void Download(object obj)
 {
  Stream httpFileStream = null, localFileStram = null;
  try
  {
   int[] ran = obj as int[];
   string tmpFileBlock = System.IO.Path.GetTempPath() + Thread.CurrentThread.Name + ".tmp";
   _tempFiles.Add(tmpFileBlock);
   HttpWebRequest httprequest = (HttpWebRequest)WebRequest.Create(_fileUrl);
   httprequest.AddRange(ran[0], ran[1]);
   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);
    lock (locker) _downloadSize += getByteSize;
    localFileStram.Write(by, 0, getByteSize);
    getByteSize = httpFileStream.Read(by, 0, (int)by.Length);
   }
   lock (locker) _threadCompleteNum++;
  }
  catch (Exception ex)
  {
   throw new Exception(ex.Message.ToString());
  }
  finally
  {
   if (httpFileStream != null) httpFileStream.Dispose();
   if (localFileStram != null) localFileStram.Dispose();
  }
  if (_threadCompleteNum == _threadNum)
  {
   Complete();
   _isComplete = true;
  }
 }
 /// <summary>
 /// 下载完成后合并文件块
 /// </summary>
 private void Complete()
 {
  Stream mergeFile = new FileStream(@_savePath, 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();
 }
}
}

调用：

string httpUrl = @"http://172.28.98.96/fdimsservice/2.rar";
string saveUrl = System.Environment.GetFolderPath(Environment.SpecialFolder.Desktop) + "//" + System.IO.Path.GetFileName(httpUrl);
int threadNumber = 5;
MultiDownload md = new MultiDownload(threadNumber, httpUrl, saveUrl);
md.Start();

希望本文所述对大家的C#程序设计有所帮助。