class Program
    {
        static void Main(string[] args)
        {
            //缓存的配置
            MemoryCacheOptions cacheOps = new MemoryCacheOptions()
            {
                //缓存最大为100份
                //##注意netcore中的缓存是没有单位的，缓存项和缓存的相对关系
                SizeLimit = 100,
                //缓存满了时，压缩20%（即删除20份优先级低的缓存项）
                CompactionPercentage = 0.2,
                //两秒钟查找一次过期项
                ExpirationScanFrequency = TimeSpan.FromSeconds(3)
            };
            MemoryCache myCache = new MemoryCache(cacheOps);

            //单个缓存项的配置
            MemoryCacheEntryOptions cacheEntityOps = new MemoryCacheEntryOptions()
            {
                //绝对过期时间1
                //AbsoluteExpiration = new DateTimeOffset(DateTime.Now.AddSeconds(2)),
                //绝对过期时间2
                //AbsoluteExpirationRelativeToNow=TimeSpan.FromSeconds(3),
                //相对过期时间
                SlidingExpiration = TimeSpan.FromSeconds(3),
                //优先级，当缓存压缩时会优先清除优先级低的缓存项
                Priority = CacheItemPriority.Low,//Low,Normal,High,NeverRemove
                //缓存大小占1份
                Size = 1
            };
            //注册缓存项被清除时的回调，可以注册多个回调
            cacheEntityOps.RegisterPostEvictionCallback((key, value, reason, state) =>
            {
                Console.WriteLine($"回调函数输出【键:{key},值:{value},被清除的原因:{reason}】");
            });

            myCache.Set("mykey", "myvalue", cacheEntityOps);
            Console.WriteLine($"mykey的值：{myCache.Get("mykey") ?? "mykey缓存被清除了"}");
            Console.WriteLine("------------------暂停3秒");
            Thread.Sleep(3000);
            Console.WriteLine($"mykey的值：{myCache.Get("mykey") ?? "mykey缓存被清除了"}");

            Console.ReadKey();
        }
    }
}