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。