一文搞懂MemoryCache 清除全部缓存的方法

 public class CacheWrapper
    {
        private readonly IMemoryCache _memoryCache;
        private CancellationTokenSource _resetCacheToken = new();

        public CacheWrapper(IMemoryCache memoryCache)
        {
            _memoryCache = memoryCache;
        }

        public void Add(object key, object value, MemoryCacheEntryOptions memoryCacheEntryOptions)
        {
            using var entry = _memoryCache.CreateEntry(key);
            entry.SetOptions(memoryCacheEntryOptions);
            entry.Value = value;

            // add an expiration token that allows us to clear the entire cache with a single method call
            entry.AddExpirationToken(new CancellationChangeToken(_resetCacheToken.Token));
        }

        public object Get(object key)
        {
            return _memoryCache.Get(key);
        }

        public void Remove(object key)
        {
            _memoryCache.Remove(key);
        }

        public void Clear()
        {
            _resetCacheToken.Cancel(); // this triggers the CancellationChangeToken to expire every item from cache

            _resetCacheToken.Dispose(); // dispose the current cancellation token source and create a new one
            _resetCacheToken = new CancellationTokenSource();
        }
    }

        [TestMethod()]
        public void ClearTest()
        {
            var memCache = new MemoryCache(new MemoryCacheOptions());
            var wrapper = new CacheWrapper(memCache);

            for (int i = 0; i < 10; i++)
            {
                wrapper.Add(i.ToString(), new object(), new MemoryCacheEntryOptions());
            }

            Assert.IsNotNull(wrapper.Get("1"));
            Assert.IsNotNull(wrapper.Get("9"));

            wrapper.Clear();

            for (int i = 0; i < 10; i++)
            {
                Assert.IsNull(wrapper.Get(i.ToString()));
            }

            for (int i = 0; i < 10; i++)
            {
                wrapper.Add(i.ToString(), new object(), new MemoryCacheEntryOptions());
            }

            Assert.IsNotNull(wrapper.Get("1"));
            Assert.IsNotNull(wrapper.Get("9"));

            wrapper.Clear();

            for (int i = 0; i < 10; i++)
            {
                Assert.IsNull(wrapper.Get(i.ToString()));
            }

        }

 /// Remove at least the given percentage (0.10 for 10%) of the total entries (or estimated memory?), according to the following policy:
        /// 1. Remove all expired items.
        /// 2. Bucket by CacheItemPriority.
        /// 3. Least recently used objects.
        /// ?. Items with the soonest absolute expiration.
        /// ?. Items with the soonest sliding expiration.
        /// ?. Larger objects - estimated by object graph size, inaccurate.
MemoryCache.Compact(double percentage);

[TestMethod()]
        public void CompactTest()
        {
            var memCache = new MemoryCache(new MemoryCacheOptions());

            for (int i = 0; i < 10; i++)
            {
                memCache.Set(i.ToString(), new object(), new MemoryCacheEntryOptions());
            }

            Assert.IsNotNull(memCache.Get("1"));
            Assert.IsNotNull(memCache.Get("9"));

            memCache.Compact(1);

            for (int i = 0; i < 10; i++)
            {
                Assert.IsNull(memCache.Get(i.ToString()));
            }

            for (int i = 0; i < 10; i++)
            {
                memCache.Set(i.ToString(), new object(), new MemoryCacheEntryOptions());
            }

            Assert.IsNotNull(memCache.Get("1"));
            Assert.IsNotNull(memCache.Get("9"));

            memCache.Compact(1);

            for (int i = 0; i < 10; i++)
            {
                Assert.IsNull(memCache.Get(i.ToString()));
            }
        }