download程序c#源码，支持断点续传.txt

用c语言编制的断点续传的源文件

    class Downfile
    { 
        public Downfile(string url,string username,string userpwd,string savename,string proxyip,string proxyport)
        {
            Durl = url;
            Dusername = username;
            Duserpwd = userpwd;
            Dsavename = savename;
            Dproxyip = proxyip;
            Dproxyport = proxyport;
        }

        public Downfile(string url, string username, string userpwd, string savename)
        {
            Durl = url;
            Dusername = username;
            Duserpwd = userpwd;
            Dsavename = savename;
        }

        public void Work()//download file no matter the file is exist or not
        {
            try
            {
                Uri uri = new Uri(Durl);
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);

                if (!(string.IsNullOrEmpty(Dproxyip) || string.IsNullOrEmpty(Dproxyport)))
                {
                    WebProxy myproxy = new WebProxy(Dproxyip, Convert.ToInt32(Dproxyport));
                    myproxy.BypassProxyOnLocal = true;
                    request.Proxy = myproxy;
                }
 
                NetworkCredential credentials = new NetworkCredential(Dusername, Duserpwd);
                request.Credentials = credentials;
                WebResponse v = request.GetResponse();
                Stream rStream = v.GetResponseStream();



                byte[] buffer = new byte[4096];
                Stream outStream = File.Create(Dsavename);

                int len;
                do
                {
                    len = rStream.Read(buffer, 0, buffer.Length);
                    if (len > 0)
                        outStream.Write(buffer, 0, len);
                } while (len > 0);

                outStream.Close();
                rStream.Close();
               
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message + "\n");
                if (WriteLog.LOgIsFine())
                    WriteLog.LogWrite(ex.Message + "\n");
            }
        }

        public void ContinueWork()//if the file is existed, The downloading may continue from the point of interruption
        {
            if (!File.Exists(Dsavename))
            {
                this.Work();
                return;
            }

//            FileInfo existfileinfo = new FileInfo(Dsavename);
           
            FileStream fs= File.OpenWrite(Dsavename);
            long lStartPos=fs.Length;
            fs.Seek(lStartPos,SeekOrigin.Current);

            try
            {

                Uri uri = new Uri(Durl);
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);

                if (!(string.IsNullOrEmpty(Dproxyip) || string.IsNullOrEmpty(Dproxyport)))
                {
                    WebProxy myproxy = new WebProxy(Dproxyip, Convert.ToInt32(Dproxyport));
                    myproxy.BypassProxyOnLocal = true;
                    request.Proxy = myproxy;
                }

                NetworkCredential credentials = new NetworkCredential(Dusername, Duserpwd);
                request.Credentials = credentials;
                if (lStartPos > 0)
                    request.AddRange((int)lStartPos);

                WebResponse v = request.GetResponse();
                Stream rStream = v.GetResponseStream();
                byte[] buffer = new byte[4096];
                // Stream outStream = File.Create(Dsavename);

                int len;
                do
                {
                    len = rStream.Read(buffer, 0, buffer.Length);
                    if (len > 0)
                        fs.Write(buffer, 0, len);
                } while (len > 0);

                fs.Close();
                rStream.Close();

                
            }
            catch (Exception ex)
            {
                fs.Close();
                Console.WriteLine(ex.Message + "\n");
                if (WriteLog.LOgIsFine())
                    WriteLog.LogWrite(ex.Message + "\n");
            }
            
        }

        private string Durl;
        private string Dusername;
        private string Duserpwd;
        private string Dsavename;
        private string Dproxyip = "";
        private string Dproxyport = null;
    }

    static class WriteLog
    {
        public static void LogOpen(string filename)
        {
            logsw = new StreamWriter(filename, true, System.Text.Encoding.UTF8);
            logsw.AutoFlush = true;
        }
        public static void LogWrite(string contents)
        {
            logsw.Write(contents);
        }
        public static void LogClose()
        {
             logsw.Flush();
             logsw.Close();
        }
        public static bool LOgIsFine()
        {
            if (logsw == null)
                return false;
            return true;
        }
        private static StreamWriter logsw = null;
    }