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。

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