获取服务器时间

就以百度为例吧,但不仅限百度,任何网站应该都可以通过获取webrequest的文件头来取到服务器的响应时间

private string getbaidu()        {            WebRequest request = null;            WebResponse response = null;            WebHeaderCollection headerCollection = null;            string datetime = string.Empty;            try            {                request = WebRequest.Create("http://www.baidu.com");                request.Timeout = 120000;                request.Credentials = CredentialCache.DefaultCredentials;                response = (WebResponse)request.GetResponse();                headerCollection = response.Headers;                foreach (var h in headerCollection.AllKeys)                { if (h == "Date") { datetime = headerCollection[h]; break; } }                return datetime;            }            catch (Exception ex) { return datetime; }            finally            {                if (request != null)                { request.Abort(); }                if (response != null)                { response.Close(); }                if (headerCollection != null)                { headerCollection.Clear(); }            }        }