本文实例讲述了C#实现文件断点续传下载的方法。分享给大家供大家参考。具体实现方法如下：

using System; using System.Data; using System.Configuration; using System.Web; using System.Web.Security; using System.IO; using System.Text; using System.Net; namespace simpleDemo { class Program { /// <summary> /// 下载文件保留字 /// </summary> public static string PERSIST_EXP = ".cdel"; /// <summary> public static void Main(string[] args) { string path = "D:aa.txt"; string ec = getFileEncoding(path, "GB2312"); print("coding: " + ec); // string content = fileReader(path, Encoding.GetEncoding(ec)); // print(content); //fileWriter(path, "测试内容11", Encoding.GetEncoding(ec)); string url = "http://www.XXX.com/20120920172200024.flv"; string path1 = "D:aa1.flv"; download(url, path1); //gapDownload(url, path1); //t(url); } public static void t(string url) { HttpWebRequest request = (System.Net.HttpWebRequest)HttpWebRequest.Create(url); //WebResponse response = httpClient.CreateGetHttpResponse(url, 3000, null, null); try { WebResponse response = request.GetResponse(); WebHeaderCollection headers = response.Headers; print(response.ContentLength); request = (System.Net.HttpWebRequest)HttpWebRequest.Create(url); request.AddRange(11); //设置Range值 WebResponse response1 = request.GetResponse(); print(response1.ContentLength); foreach (string key in headers) { print(key + "----- " + headers.Get(key)); } string disposition = headers.Get("Content-Disposition"); print(disposition); }catch(Exception e){ print(e.Message); } //string fileName = disposition.Substring(disposition.IndexOf(""")); //print(fileName); } public static void download(string url, string path) { if (File.Exists(path)) { print("文件己存在！是否重新下载？"); return; } else { path = path + PERSIST_EXP; simpleDownload(url,path);//开始下载 } } /// <summary> /// 下载网络资源(支持断点续传) /// </summary> /// <param name="url"></param> /// <param name="path"></param> public static void simpleDownload(string url, string path) { HttpWebRequest request = httpClient.getWebRequest(url, 0); WebResponse response = null; FileStream writer = new FileStream(path, FileMode.OpenOrCreate, FileAccess.Write); long lStartPos = writer.Length; ;//当前文件大小 long currentLength = 0; long totalLength = 0;//总大小 if (File.Exists(path))//断点续传 { response = request.GetResponse(); long sTotal = response.ContentLength; if (sTotal == lStartPos) { close(writer); File.Move(path, path.Replace(PERSIST_EXP, "")); print("下载完成!"); return; } request = httpClient.getWebRequest(url, (int)lStartPos); //设置Range值 writer.Seek(lStartPos, SeekOrigin.Begin);//指针跳转 response = request.GetResponse(); totalLength = response.ContentLength + lStartPos; //总长度 currentLength = lStartPos; //当前长度 } else { response = request.GetResponse(); totalLength = response.ContentLength; } Stream reader = response.GetResponseStream(); byte[] buff = new byte[1024]; int c = 0; //实际读取的字节数 while ((c = reader.Read(buff, 0, buff.Length)) > 0) { currentLength += c; writer.Write(buff, 0, c); progressBar(currentLength, totalLength);//进度条 writer.Flush(); } close(writer); if (currentLength == totalLength) { File.Move(path, path.Replace(PERSIST_EXP, "")); print("下载完成!"); } if (reader != null) { reader.Close(); reader.Dispose(); response.Close(); } } private static void close(FileStream writer) { if (writer != null) { writer.Close(); writer.Dispose(); } } /// <summary> /// 进度条 /// </summary> /// <param name="currentLength">当前长度</param> /// <param name="totalLength">总长度</param> public static void progressBar(Object currentLength, Object totalLength) { double aaa = System.Convert.ToDouble(currentLength); double bbb = System.Convert.ToDouble(totalLength); print(currentLength + "/" + totalLength + "__" + (aaa / bbb).ToString("0.00 %")); } /// <summary> /// 系统输出 /// </summary> /// <param name="obj"></param> public static void print(Object obj){ Console.WriteLine(obj); } public static void printStr(string[] str) { foreach (string d in str) { print(d); } } /// <summary> /// 文件写 /// </summary> /// <param name="path">文件路径</param> /// <param name="content">要写入的内容</param> public static void fileWriter(string path,string content,Encoding encoding) { if (File.Exists(path)) { StreamWriter sw = new StreamWriter(path, true, encoding); sw.WriteLine(content); sw.Flush(); sw.Close(); } } /// <summary> /// 读文件，返回内容 /// </summary> /// <param name="path">文件路径</param> /// <param name="enCoding">默认编码格式</param> /// <returns></returns> public static string fileReader(string path,Encoding enCoding) { StringBuilder sb = new StringBuilder(); if(enCoding == null){ enCoding = Encoding.Default; } //读取文件 StreamReader sr = new StreamReader(path, enCoding); string s = ""; while ((s = sr.ReadLine()) != null) { sb.AppendLine(s); } if(sr != null) sr.Close(); return sb.ToString(); } /// <summary> /// 获取文件编码格式 /// </summary> /// <param name="path">文件路径</param> /// <param name="defaultEncoding">默认编码</param> /// <returns></returns> public static string getFileEncoding(string path, string defaultEncoding) { string ed = defaultEncoding; if (File.Exists(path)) { FileStream fs = new FileStream(path, FileMode.Open); ed = GetEncoding(fs, defaultEncoding); if (fs != null) fs.Close(); } return ed; } /// <summary> /// 取得一个文本文件流的编码方式。 /// </summary> /// <param name="stream">文本文件流。</param> /// <param name="defaultEncoding">默认编码方式。当该方法无法从文件的头部取得有效的前导符时，将返回该编码方式。</param> /// <returns></returns> public static string GetEncoding(FileStream stream, string defaultEncoding) { string targetEncoding = defaultEncoding; if (stream != null && stream.Length >= 2) { //保存文件流的前4个字节 byte byte1 = 0; byte byte2 = 0; byte byte3 = 0; byte byte4 = 0; //保存当前Seek位置 long origPos = stream.Seek(0, SeekOrigin.Begin); stream.Seek(0, SeekOrigin.Begin); int nByte = stream.ReadByte(); byte1 = Convert.ToByte(nByte); byte2 = Convert.ToByte(stream.ReadByte()); if (stream.Length >= 3) { byte3 = Convert.ToByte(stream.ReadByte()); } if (stream.Length >= 4) { byte4 = Convert.ToByte(stream.ReadByte()); } //根据文件流的前4个字节判断Encoding //Unicode {0xFF, 0xFE}; //BE-Unicode {0xFE, 0xFF}; //UTF8 = {0xEF, 0xBB, 0xBF}; if (byte1 == 0xFE && byte2 == 0xFF)//UnicodeBe { targetEncoding = Encoding.BigEndianUnicode.BodyName; } if (byte1 == 0xFF && byte2 == 0xFE && byte3 != 0xFF)//Unicode { targetEncoding = Encoding.Unicode.BodyName; } if (byte1 == 0xEF && byte2 == 0xBB && byte3 == 0xBF)//UTF8 { targetEncoding = Encoding.UTF8.BodyName; } //恢复Seek位置 stream.Seek(origPos, SeekOrigin.Begin); } return targetEncoding; } } } using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Net; using System.Net.Security; using System.Security.Cryptography.X509Certificates; using System.IO; namespace simpleDemo { /// <summary> /// 公用 Http 请求类 /// </summary> class httpClient { /// <summary> /// 获取基础WebRequest /// </summary> /// <param name="url">请求地址</param> /// <param name="lStartPos">请求的开始位置</param> /// <returns></returns> public static HttpWebRequest getWebRequest(string url, int lStartPos) { HttpWebRequest request = null; try { request = (System.Net.HttpWebRequest)HttpWebRequest.Create(url); request.AddRange(lStartPos); //设置Range值 } catch (Exception ex) { Program.print(ex.Message); } return request; } } }

希望本文所述对大家的C#程序设计有所帮助。