HttpWebRequest q = (HttpWebRequest)WebRequest.Create("http://www.yunxingwenhua.com.cn/2011011703005.mp3");
        q.Method = "post";
        q.ContentType = "application/x-www-form-urlencoded";
        Stream s = q.GetRequestStream();
        BinaryReader b = new BinaryReader(s);                   //流不可写
        FileStream fs = new FileStream("G:\\a.mp3", FileMode.Create, FileAccess.Write);
        fs.Write(b.ReadBytes((int)q.ContentLength), 0, (int)q.ContentLength);
        fs.Close();
        b.Close();
        s.Close();请问为什么流不可写,哪儿错了