ObjectCache cache = MemoryCache.Default;    //得到MemoryCache全局实例

            string myData = cache["mydata"] as string;  //访问缓存数据

            if (myData == null)

            {

                 CacheItemPolicy policy = new CacheItemPolicy();  //创建缓存项策略

                 //过期时间设置,以下两种只能设置一种

                policy.AbsoluteExpiration = new DateTimeOffset(DateTime.Now.AddMinutes()); //设定某个时间过后将逐出缓存

                policy.SlidingExpiration = new TimeSpan(, , );    //设定某个时间段内未被访问将逐出缓存

                //逐出通知,以下两种只能设置一种

                 policy.UpdateCallback = arguments => { Console.WriteLine("即将逐出缓存" + arguments.Key); };  //逐出前执行的方法

                //policy.RemovedCallback = arguments => { Console.WriteLine("已经逐出缓存" + arguments.CacheItem.Key); };  //逐出后执行的方法

                //缓存监视类有4种

                //CacheEntryChangeMonitor;

                //FileChangeMonitor;

                //HostFileChangeMonitor;

                //SqlChangeMonitor;

                //用法

                //List<string> filePaths = new List<string>();

                //filePaths.Add("c:\\cache\\example.txt");

                //policy.ChangeMonitors.Add(new HostFileChangeMonitor(filePaths));

                 myData = "缓存数据"+DateTime.Now.ToShortTimeString();

                 cache.Set("mydata", myData, policy);  //设置缓存数据,如果已存在则覆盖

            }

            Console.WriteLine("得到" + myData);