斷點傳輸

string strFileName="d:\\aa.rar";
        string strUrl="http://192.168.1.9/Artmall/HML.rar";
        public Class1()
        {
        }

        public void upFile()
        {
            //打開上次下載文件或新建文件
            long iStartPos=0;
            System.IO.FileStream fs;
            if(System.IO.File.Exists(strFileName))
            {
                fs = System.IO.File.OpenWrite(strFileName);
                iStartPos = fs.Length;
                fs.Seek(iStartPos,System.IO.SeekOrigin.Current);//移動文件流中的當前指針
            }
            else
            {
                fs = new System.IO.FileStream(strFileName,System.IO.FileMode.Create);
                iStartPos=0;
            }
            //打開網絡連接
            try
            {
                System.Net.HttpWebRequest request = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create(strUrl);
                if(iStartPos>0)
                    request.AddRange((int)iStartPos);//    設置Range的值,Range表示從何處開始下載
                //向服務器請求、獲得服務器回應數據流
                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();
            }
            catch(System.Exception exc)
            {
                fs.Close();
                throw new Exception("It's Error for Down Files--->" + exc.ToString());
            }
        }