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。