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。

 1  static bool UrlIsExist(String url)
 2         {
 3             System.Uri u = null;
 4             try
 5             {
 6                 u = new Uri(url);
 7             }
 8             catch { return false; }
 9             bool isExist = false;
10             System.Net.HttpWebRequest r = System.Net.HttpWebRequest.Create(u) as System.Net.HttpWebRequest;
11             r.Method = "HEAD";
12             try
13             {
14                 System.Net.HttpWebResponse s = r.GetResponse() as System.Net.HttpWebResponse;
15                 if (s.StatusCode == System.Net.HttpStatusCode.OK)
16                 {
17                     isExist = true;
18                 }
19             }
20             catch (System.Net.WebException x)
21             {
22                 try
23                 {
24                     isExist = ((x.Response as System.Net.HttpWebResponse).StatusCode != System.Net.HttpStatusCode.NotFound);
25                 }
26                 catch { isExist = (x.Status == System.Net.WebExceptionStatus.Success); }
27             }
28             return isExist;
29         }

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。

 1         static bool UrlIsExist(string URL)
 2         {
 3             try
 4             {
 5                 System.Net.WebRequest request = System.Net.WebRequest.Create(URL);
 6                 request.Timeout = 10000;
 7                 System.Net.WebResponse response = request.GetResponse();
 8                 return true;
 9             }
10             catch
11             {
12                 return false;
13             }
14         }

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