C#实现文件断点续传下载的方法

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。