cachehelper調(diào)用時(shí)總是出錯(cuò)時(shí)為什么，提示是：System.NullReferenceException: 未將對(duì)象引用設(shè)置到對(duì)象的實(shí)例。郁悶了很久了.    public static Cache cache = new Cache();    public static void Insert(string key, object obj, double Minutes)    {        if (obj != null)        {            cache.Insert(key, obj, null, DateTime.Now.AddMinutes(Minutes), Cache.NoSlidingExpiration, CacheItemPriority.High, null);        }    }DataSet ds;        if (Cache["Rss"] == null)        {            string sqlStr = "select top 50 co.id,co.title,co.time,co.content,ca.category from [content] co,[category] ca where co.cateid=ca.id order by co.id desc";            ds = SQLHelper.Query(sqlStr);            CacheHelper.CacheInsertAddMinutes("Rss", ds, 10);        }錯(cuò)誤是：異常詳細(xì)信息: System.NullReferenceException: 未將對(duì)象引用設(shè)置到對(duì)象的實(shí)例。