C#实现断点续传

using System;
using System.Collections.Generic;
using System.Text;
using System.Net;
 
namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            string StrFileName = "c:\\mathsetup.rar"; //根据实际情况设置 
            string StrUrl = ""; //根据实际情况设置 
 
            //打开上次下载的文件或新建文件 
            long lStartPos = 0;
            System.IO.FileStream fs;
            if (System.IO.File.Exists(StrFileName))
            {
                fs = System.IO.File.OpenWrite(StrFileName);
                lStartPos = fs.Length;
                fs.Seek(lStartPos, System.IO.SeekOrigin.Current); //移动文件流中的当前指针 
            }
            else
            {
                fs = new System.IO.FileStream(StrFileName, System.IO.FileMode.Create);
                lStartPos = 0;
            }
 
            //打开网络连接 
            try
            {
                System.Net.HttpWebRequest request = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create(StrUrl);
                if (lStartPos > 0)
                    request.AddRange((int)lStartPos); //设置Range值 
 
                //向服务器请求，获得服务器回应数据流 
                System.IO.Stream ns = request.GetResponse().GetResponseStream();
                byte[] nbytes = new byte[512];
                int nReadSize = 0;
                nReadSize = ns.Read(nbytes, 0, 512);
                while (nReadSize > 0)
                {
                    fs.Write(nbytes, 0, nReadSize);
                    nReadSize = ns.Read(nbytes, 0, 512);
                }
                fs.Close();
                ns.Close();
                Console.WriteLine("下载完成");
            }
            catch (Exception ex)
            {
                fs.Close();
                Console.WriteLine("下载过程中出现错误:" + ex.ToString());
            }
 
            Console.Read();
        }
    }
}