c# 实现轮询算法实例代码

 public class CountdownHelper  {     private const int CacheSlidingExpirationHour = 2;     private const string CountdownCurrentIndexCacheName = "OnlineMeetingCountdownCurrentIndex";     private static IAppLog log = AppLoggerManager.GetLogger(typeof(CountdownHelper));     private static Cache m_cache = HttpContext.Current.Cache;     private static object m_objCountdownCurrentIndexLock = new object();     private static int[] m_snIntervalSecond = new int[] { 0, 1 , 1 , 1}; //1显示 0不显示      public CountdownHelper()     {     }     public int GetCountdownAddedSecond()     {       lock (m_objCountdownCurrentIndexLock)       {         int nCountdownCurrentIndex = 0;          try         {           object objCountdownCurrentIndex = m_cache[CountdownCurrentIndexCacheName];           if (objCountdownCurrentIndex == null)           {             //如果需要加缓存的，就用下面的             //m_cache.Insert(CountdownCurrentIndexCacheName, 1, null, Cache.NoAbsoluteExpiration, TimeSpan.FromHours(CacheSlidingExpirationHour), CacheItemPriority.NotRemovable, null);             //不用加缓存的用下面的             m_cache.Insert(CountdownCurrentIndexCacheName, 1, null, Cache.NoAbsoluteExpiration, Cache.NoSlidingExpiration, CacheItemPriority.NotRemovable, null);           }           else           {             nCountdownCurrentIndex = (int)objCountdownCurrentIndex;             if (nCountdownCurrentIndex == m_snIntervalSecond.Length - 1)             {               m_cache[CountdownCurrentIndexCacheName] = 0;             }             else             {               m_cache[CountdownCurrentIndexCacheName] = nCountdownCurrentIndex + 1;             }           }            return m_snIntervalSecond[nCountdownCurrentIndex];        }        catch (Exception __error)         {           //如果需要记录错误日志的，可以记录到这里，我这里没有加           //log.Error("功能介绍GetCountdownAddedSecond：" + __error.Message);           if (nCountdownCurrentIndex > m_snIntervalSecond.Length - 1)           {             nCountdownCurrentIndex = m_snIntervalSecond.Length - 1;          }           return m_snIntervalSecond[nCountdownCurrentIndex];         }       }     }    }

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<!--轮询曝光-->   $.post("/Topic/GetCountdownAddedSecond", function (data) {    if (data) {       if (data.num == 1) {        var img_html = "<img src=/"https://d_directed_treatment =?/ment/" style=/"display:none;/">";         $("#adver").html(img_html);       }     }   }, "json");