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 = 10000;
                System.Net.WebResponse response = request.GetResponse();
                return true;
            }
            catch
            {
                return false;
            }
        }

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