.net core3.1中使用缓存MemoryCache

nugt包依赖：

• 1.Microsoft.Extensions.Caching.Abstractions
• 2.Microsoft.Extensions.Caching.Memory

封装的帮助类

添加类库Snblog.Cache

新建文件 Cache

新建帮助类 CacheManager.cs

using Microsoft.Extensions.Caching.Memory;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Reflection;
using System.Text;

namespace Snblog.Cache.Cache
{
 public class CacheManager
    {
        public static CacheManager Default = new CacheManager();
        public  TimeSpan time = new TimeSpan(00, 00, 01, 0); //缓存过期时间
        private IMemoryCache _cache = new MemoryCache(new MemoryCacheOptions());

        /// <summary>
        /// 判断是否在缓存中
        /// </summary>
        /// <param name="key">关键字</param>
        /// <returns></returns>
        public bool IsInCache(string key)
        {
            List<string> keys = GetAllKeys();
            foreach (var i in keys)
            {
                if (i == key) return true;
            }
            return false;
        }

        /// <summary>
        /// 获取所有缓存键
        /// </summary>
        /// <returns></returns>
        public List<string> GetAllKeys()
        {
            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;
        }

        /// <summary>
        /// 获取所有的缓存值
        /// </summary>
        /// <returns></returns>
        public List<T> GetAllValues<T>()
        {
            var cacheKeys = GetAllKeys();
            List<T> vals = new List<T>();
            cacheKeys.ForEach(i =>
            {
                T t;
                if (_cache.TryGetValue<T>(i, out t))
                {
                    vals.Add(t);
                }
            });
            return vals;
        }
        /// <summary>
        /// 取得缓存数据
        /// </summary>
        /// <typeparam name="T">类型值</typeparam>
        /// <param name="key">关键字</param>
        /// <returns></returns>
        public T Get<T>(string key)
        {
            if (string.IsNullOrWhiteSpace(key))
                throw new ArgumentNullException(nameof(key));
            T value;
            _cache.TryGetValue<T>(key, out value);
            return value;
        }

        /// <summary>
        /// 设置缓存(永不过期)
        /// </summary>
        /// <param name="key">关键字</param>
        /// <param name="value">缓存值</param>
        public void Set_NotExpire<T>(string key, T value)
        {
            if (string.IsNullOrWhiteSpace(key))
                throw new ArgumentNullException(nameof(key));

            T v;
            if (_cache.TryGetValue(key, out v))
                _cache.Remove(key);
            _cache.Set(key, value);
        }

        /// <summary>
        /// 设置缓存(滑动过期:超过一段时间不访问就会过期,一直访问就一直不过期)
        /// </summary>
        /// <param name="key">关键字</param>
        /// <param name="value">缓存值</param>
        public void Set_SlidingExpire<T>(string key, T value, TimeSpan span)
        {
            if (string.IsNullOrWhiteSpace(key))
                throw new ArgumentNullException(nameof(key));

            T v;
            if (_cache.TryGetValue(key, out v))
                _cache.Remove(key);
            _cache.Set(key, value, new MemoryCacheEntryOptions()
            {
                SlidingExpiration = span
            });
        }

        /// <summary>
        /// 设置缓存(绝对时间过期:从缓存开始持续指定的时间段后就过期,无论有没有持续的访问)
        /// </summary>
        /// <param name="key">关键字</param>
        /// <param name="value">缓存值</param>
        public void Set_AbsoluteExpire<T>(string key, T value, TimeSpan span)
        {
            if (string.IsNullOrWhiteSpace(key))
                throw new ArgumentNullException(nameof(key));

            T v;
            if (_cache.TryGetValue(key, out v))
                _cache.Remove(key);
            _cache.Set(key, value, span);
        }

        /// <summary>
        /// 设置缓存(绝对时间过期+滑动过期:比如滑动过期设置半小时,绝对过期时间设置2个小时，那么缓存开始后只要半小时内没有访问就会立马过期,如果半小时内有访问就会向后顺延半小时，但最多只能缓存2个小时)
        /// </summary>
        /// <param name="key">关键字</param>
        /// <param name="value">缓存值</param>
        /// <param name="slidingSpan"></param>
        /// <param name="absoluteSpan"></param>
        public void Set_SlidingAndAbsoluteExpire<T>(string key, T value, TimeSpan slidingSpan, TimeSpan absoluteSpan)
        {
            if (string.IsNullOrWhiteSpace(key))
                throw new ArgumentNullException(nameof(key));

            T v;
            if (_cache.TryGetValue(key, out v))
                _cache.Remove(key);
            _cache.Set(key, value, new MemoryCacheEntryOptions()
            {
                SlidingExpiration = slidingSpan,
                AbsoluteExpiration = DateTimeOffset.Now.AddMilliseconds(absoluteSpan.Milliseconds)
            });
        }

        /// <summary>
        /// 移除缓存
        /// </summary>
        /// <param name="key">关键字</param>
        public void Remove(string key)
        {
            if (string.IsNullOrWhiteSpace(key))
                throw new ArgumentNullException(nameof(key));

            _cache.Remove(key);
        }

        /// <summary>
        /// 释放
        /// </summary>
        public void Dispose()
        {
            if (_cache != null)
                _cache.Dispose();
            GC.SuppressFinalize(this);
        }
    }

}

Service中使用

        //创建内存缓存对象
        private static CacheManager _cache = new CacheManager();
        
         /// <summary>
        /// 返回总条数
        /// </summary>
        /// <returns></returns>
        public int GetArticleCount()
        {
            int result;
            if (_cache.IsInCache("GetArticleCount")) //是否存在缓存
            {
                result = _cache.Get<int>("GetArticleCount");//读缓存值
                if (result <= 0)
                {
                    _cache.Set_AbsoluteExpire("GetArticleCount", CreateService<SnArticle>().Count(), _cache.time);//设置缓存
                    result = _cache.Get<int>("GetArticleCount");
                }
            }
            else
            {
                _cache.Set_AbsoluteExpire("GetArticleCount", CreateService<SnArticle>().Count(), _cache.time); //设置缓存
                result = _cache.Get<int>("GetArticleCount");
            }
            return result;
        }