.NET Core MemoryCache緩存獲取全部緩存鍵

在Core中不能使用原HttpRuntime.Cache緩存，改為MemoryCache（Microsoft.Extensions.Caching.Memory）.

現MemoryCache新版為2.0.1，於原HttpRuntime.Cache擴展方法基本相同，但裡面沒有查詢全部鍵(key) 的擴展，要想查詢可通過反射查找

代碼如下:

       public List<string> GetCacheKeys()
        {
            const BindingFlags flags = BindingFlags.Instance | BindingFlags.NonPublic;
            var entries = Cache.GetType().GetField("_entries", flags).GetValue(Cache);
            var cacheItems = entries as IDictionary;
            var keys = new List<string>();
            if (cacheItems == null) return keys;
            foreach (DictionaryEntry cacheItem in cacheItems)
            {
                keys.Add(cacheItem.Key.ToString());
            }
            return keys;
        }

這樣我們就能獲取到全部的鍵.

整體MemoryCacheHelper類如下:

public class MemoryCacheHelper
    {
        private static readonly MemoryCache Cache = new MemoryCache(new MemoryCacheOptions());

        /// <summary>
        /// 驗證緩存項是否存在
        /// </summary>
        /// <param name="key">緩存Key</param>
        /// <returns></returns>
        public bool Exists(string key)
        {
            if (key == null)
                throw new ArgumentNullException(nameof(key));
            return Cache.TryGetValue(key, out _);
        }

        /// <summary>
        /// 添加緩存
        /// </summary>
        /// <param name="key">緩存Key</param>
        /// <param name="value">緩存Value</param>
        /// <param name="expiresSliding">滑動過期時長（如果在過期時間內有操作，則以當前時間點延長過期時間）</param>
        /// <param name="expiressAbsoulte">絕對過期時長</param>
        /// <returns></returns>
        public bool Set(string key, object value, TimeSpan expiresSliding, TimeSpan expiressAbsoulte)
        {
            if (key == null)
                throw new ArgumentNullException(nameof(key));
            if (value == null)
                throw new ArgumentNullException(nameof(value));

            Cache.Set(key, value,
                new MemoryCacheEntryOptions().SetSlidingExpiration(expiresSliding)
                    .SetAbsoluteExpiration(expiressAbsoulte));
            return Exists(key);
        }

        /// <summary>
        /// 添加緩存
        /// </summary>
        /// <param name="key">緩存Key</param>
        /// <param name="value">緩存Value</param>
        /// <param name="expiresIn">緩存時長</param>
        /// <param name="isSliding">是否滑動過期（如果在過期時間內有操作，則以當前時間點延長過期時間）</param>
        /// <returns></returns>
        public bool Set(string key, object value, TimeSpan expiresIn, bool isSliding = false)
        {
            if (key == null)
                throw new ArgumentNullException(nameof(key));
            if (value == null)
                throw new ArgumentNullException(nameof(value));

            Cache.Set(key, value,
                isSliding
                    ? new MemoryCacheEntryOptions().SetSlidingExpiration(expiresIn)
                    : new MemoryCacheEntryOptions().SetAbsoluteExpiration(expiresIn));

            return Exists(key);
        }

        #region 刪除緩存

        /// <summary>
        /// 刪除緩存
        /// </summary>
        /// <param name="key">緩存Key</param>
        /// <returns></returns>
        public void Remove(string key)
        {
            if (key == null)
                throw new ArgumentNullException(nameof(key));

            Cache.Remove(key);
        }

        /// <summary>
        /// 批量刪除緩存
        /// </summary>
        /// <returns></returns>
        public void RemoveAll(IEnumerable<string> keys)
        {
            if (keys == null)
                throw new ArgumentNullException(nameof(keys));

            keys.ToList().ForEach(item => Cache.Remove(item));
        }
        #endregion

        #region 獲取緩存

        /// <summary>
        /// 獲取緩存
        /// </summary>
        /// <param name="key">緩存Key</param>
        /// <returns></returns>
        public T Get<T>(string key) where T : class
        {
            if (key == null)
                throw new ArgumentNullException(nameof(key));

            return Cache.Get(key) as T;
        }

        /// <summary>
        /// 獲取緩存
        /// </summary>
        /// <param name="key">緩存Key</param>
        /// <returns></returns>
        public object Get(string key)
        {
            if (key == null)
                throw new ArgumentNullException(nameof(key));

            return Cache.Get(key);
        }

        /// <summary>
        /// 獲取緩存集合
        /// </summary>
        /// <param name="keys">緩存Key集合</param>
        /// <returns></returns>
        public IDictionary<string, object> GetAll(IEnumerable<string> keys)
        {
            if (keys == null)
                throw new ArgumentNullException(nameof(keys));

            var dict = new Dictionary<string, object>();
            keys.ToList().ForEach(item => dict.Add(item, Cache.Get(item)));
            return dict;
        }
        #endregion

        /// <summary>
        /// 刪除所有緩存
        /// </summary>
        public void RemoveCacheAll()
        {
            var l = GetCacheKeys();
            foreach (var s in l)
            {
                Remove(s);
            }
        }

        /// <summary>
        /// 刪除匹配到的緩存
        /// </summary>
        /// <param name="pattern"></param>
        /// <returns></returns>
        public void RemoveCacheRegex(string pattern)
        {
            IList<string> l = SearchCacheRegex(pattern);
            foreach (var s in l)
            {
                Remove(s);
            }
        }

        /// <summary>
        /// 搜索 匹配到的緩存
        /// </summary>
        /// <param name="pattern"></param>
        /// <returns></returns>
        public IList<string> SearchCacheRegex(string pattern)
        {
            var cacheKeys = GetCacheKeys();
            var l = cacheKeys.Where(k => Regex.IsMatch(k, pattern)).ToList();
            return l.AsReadOnly();
        }

        /// <summary>
        /// 獲取所有緩存鍵
        /// </summary>
        /// <returns></returns>
        public List<string> GetCacheKeys()
        {
            const BindingFlags flags = BindingFlags.Instance | BindingFlags.NonPublic;
            var entries = Cache.GetType().GetField("_entries", flags).GetValue(Cache);
            var cacheItems = entries as IDictionary;
            var keys = new List<string>();
            if (cacheItems == null) return keys;
            foreach (DictionaryEntry cacheItem in cacheItems)
            {
                keys.Add(cacheItem.Key.ToString());
            }
            return keys;
        }
    }

 Startup.cs文件public void ConfigureServices(IServiceCollection services)方法註冊MemoryCache

services.AddMemoryCache();