参考网站：http://www.cnblogs.com/junny/archive/2012/10/30/2745978.html

 

public bool CheckUrlVisit(string url)     {               try        {            HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);            HttpWebResponse resp = (HttpWebResponse)req.GetResponse();            if (resp.StatusCode == HttpStatusCode.OK)            {
  　　　　　　　　　　resp.Close();                 return true;            }        }        catch (WebException webex)        {            return false;        }        return false;        }