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。