获取网络上的北京时间，如果大于设定的过期时间就...

设置一个过期时间 ，定义时间变量dd，dd获取网络上的北京时间，如果获取失败，就获取计算机当前时间，再比对dd与过期时间，如果dd大于过期时间，就执行...

        // 比对固定时间，看是否超时。
        private void CompareTime()
        {
            try
            {
                dd = GetBeijingTime();
                i = DateTime.Compare(dd, Convert.ToDateTime("2013-1-1 00:00:00"));
                if (i < 0)
                {
                    dd = DateTime.Today;
                }
            }
            catch
            {

            }

            i = DateTime.Compare(dd, Convert.ToDateTime("2014-5-5 00:00:00"));
            if (i > 0)
            {
                btnOpen.Enabled = false;
            }
        }

        // 获取北京时间
        public static DateTime GetBeijingTime()
        {
            //t0 = new Date().getTime();
            //nyear = 2011;
            //nmonth = 7;
            //nday = 5;
            //nwday = 2;
            //nhrs = 17;
            //nmin = 12;
            //nsec = 12;
            DateTime dt;
            WebRequest wrt = null;
            WebResponse wrp = null;
            try
            {
                wrt = WebRequest.Create("http://www.beijing-time.org/time.asp");
                wrp = wrt.GetResponse();

                string html = string.Empty;
                using (Stream stream = wrp.GetResponseStream())
                {
                    using (StreamReader sr = new StreamReader(stream, Encoding.UTF8))
                    {
                        html = sr.ReadToEnd();
                    }
                }

                string[] tempArray = html.Split(‘;‘);
                for (int i = 0; i < tempArray.Length; i++)
                {
                    tempArray[i] = tempArray[i].Replace("\r\n", "");
                }

                string year = tempArray[1].Substring(tempArray[1].IndexOf("nyear=") + 6);
                string month = tempArray[2].Substring(tempArray[2].IndexOf("nmonth=") + 7);
                string day = tempArray[3].Substring(tempArray[3].IndexOf("nday=") + 5);
                string hour = tempArray[5].Substring(tempArray[5].IndexOf("nhrs=") + 5);
                string minite = tempArray[6].Substring(tempArray[6].IndexOf("nmin=") + 5);
                string second = tempArray[7].Substring(tempArray[7].IndexOf("nsec=") + 5);
                dt = DateTime.Parse(year + "-" + month + "-" + day + " " + hour + ":" + minite + ":" + second);
            }
            catch (WebException)
            {
                return DateTime.Parse("2011-4-1");
            }
            catch (Exception)
            {
                return DateTime.Parse("2011-1-1");
            }
            finally
            {
                if (wrp != null)
                    wrp.Close();
                if (wrt != null)
                    wrt.Abort();
            }
            return dt;
        }