c# 判断网络地址是否存在

方法一：网络地址存在，有可能可以访问，也有可能不能访问。此方法用来判断地址存在。

  static bool UrlIsExist(String url)
         {
             System.Uri u = null;
             try
             {
                 u = new Uri(url);
             }
             catch { return false; }
             bool isExist = false;
             System.Net.HttpWebRequest r = System.Net.HttpWebRequest.Create(u) as System.Net.HttpWebRequest;
             r.Method = "HEAD";
             try
             {
                 System.Net.HttpWebResponse s = r.GetResponse() as System.Net.HttpWebResponse;
                 if (s.StatusCode == System.Net.HttpStatusCode.OK)
                 {
                     isExist = true;
                 }
             }
             catch (System.Net.WebException x)
             {
                 try
                 {
                     isExist = ((x.Response as System.Net.HttpWebResponse).StatusCode != System.Net.HttpStatusCode.NotFound);
                 }
                 catch { isExist = (x.Status == System.Net.WebExceptionStatus.Success); }
             }
             return isExist;
         }

方法二：地址是否有效，即是网络连接地址是否正常显示。地址有可能存在，也有可能不存在，能正常显示则说明地址是有效的，反正则是无效的。

         static bool UrlIsExist(string URL)
         {
             try
             {
                 System.Net.WebRequest request = System.Net.WebRequest.Create(URL);
                 request.Timeout = ;
                 System.Net.WebResponse response = request.GetResponse();
                 return true;
             }
             catch
             {
                 return false;
             }
         }

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