c# 判断URL是否有用

        //判断url对应的商品是否存在，存在返回真，不存在返回假

        public bool getUrlTorF(string linkUrl, string errUrl, long leng, string neiRong)
        {
            bool justInfo = false;
            req = (HttpWebRequest)WebRequest.Create(linkUrl);
            req.Method = "GET";
            req.AllowAutoRedirect = false;
            try
            {
                myResp = (HttpWebResponse)req.GetResponse();
                if (leng != 0)
                {
                    //根据内容大小来判断该商品是否有效
                    long content = myResp.ContentLength;
                    if (content < leng)
                    {
                        justInfo = true;
                    }

                }
                else
                {

                    //根据跳转页面来判断该商品是否有效
                    if (myResp.StatusCode == HttpStatusCode.Redirect)
                    {
                        string redirectUrl = myResp.GetResponseHeader("Location").ToLower();
                        if (redirectUrl == errUrl.ToLower())
                        {
                            justInfo = true;
                        }

                    }
                    //根据内容关键字来判断该商品是否有效
                    else
                    {
                        Stream mystream = (Stream)req.GetResponse().GetResponseStream();
                        StreamReader mr = new StreamReader(mystream, Encoding.GetEncoding("gb2312"));
                        if (mr.ReadToEnd().IndexOf(neiRong) >= 0 && neiRong.Trim() != "")
                        {
                            justInfo = true;
                            //Console.WriteLine("找到");
                        }
                        else if (new StreamReader(mystream, Encoding.GetEncoding("utf-8")).ReadToEnd().IndexOf(neiRong) >= 0 && neiRong.Trim() != "")
                        {
                            justInfo = true;
                        }
                    }
                }
            }
            catch (System.Exception ex)
            {
                Console.WriteLine(ex.Message);
                justInfo = true;
                // Console.WriteLine(linkUrl);
            }
            return justInfo;
        }