C# Cache缓存的应用

  public class CacheHelper
   {
       private static string fileName = @"D:\huage.txt";
       
       /// <summary>
       /// 获取Cache
       /// </summary>
       /// <param name="key"></param>
       /// <returns></returns>
        public static object GetCache(string key)
        {
            var objCache = HttpRuntime.Cache;
            return objCache[key];
        }

        /// <summary>
        /// 设置当前应用程序指定CacheKey的Cache对象值
        /// </summary>
        /// <param name="key">索引键值</param>
        /// <param name="obj">缓存对象</param>
        public static void SetCache(string key, dynamic obj)
        {
            var objCache = HttpRuntime.Cache;
            objCache.Insert(key, obj);
        }

        /// <summary>
        /// 设置当前应用程序指定CacheKey的Cache对象值
        /// </summary>
        /// <param name="key">索引键值</param>
        /// <param name="obj">缓存对象</param>
        /// <param name="absoluteExpiration">绝对过期时间 要避免可能的本地时间问题（例如从标准时间改为夏时制），请使用 <see cref="P:System.DateTime.UtcNow" /> 而不是 <see cref="P:System.DateTime.Now" /> 作为此参数值</param>
        public static void SetCache(string key, dynamic obj, DateTime absoluteExpiration)
        {
            var objCache = HttpRuntime.Cache;
            absoluteExpiration = DateTime.SpecifyKind(absoluteExpiration, DateTimeKind.Utc);
            //使用absoluteExpiration（绝对过期时间），怎相对过期时间需要为System.Web.Caching.Cache.NoSlidingExpiration
            objCache.Insert(key, obj, null, absoluteExpiration, System.Web.Caching.Cache.NoSlidingExpiration);
        }

        /// <summary>
        /// 设置当前应用程序指定CacheKey的Cache对象值
        /// </summary>
        /// <param name="key">索引键值</param>
        /// <param name="obj">缓存对象</param>
        /// <param name="slidingExpiration">最后一次访问所插入对象时与该对象过期时之间的时间间隔</param>
        public static void SetCache(string key, dynamic obj, TimeSpan slidingExpiration)
        {
            var objCache = HttpRuntime.Cache;
            //使用slidingExpiration（相对过期时间），怎相对过期时间需要为System.Web.Caching.Cache.NoAbsoluteExpiration
            objCache.Insert(key, obj, null, System.Web.Caching.Cache.NoAbsoluteExpiration, slidingExpiration);
        }

        /// <summary>
        /// 缓存依赖
        /// </summary>
        /// <param name="key">索引键值</param>
        /// <param name="value">缓存对象</param>
        public static void SetCacheByCacheDependency(string key, object value)
        {
            System.Web.Caching.CacheDependency cacheDependency = new CacheDependency(fileName);//建立缓存依赖项dp
            HttpRuntime.Cache.Insert(key, value, cacheDependency);
        }

        /// <summary>
        /// 缓存依赖获取值（不存在就取取值）
        /// </summary>
        /// <param name="key">索引键值</param>
        public static object GetCacheByCacheDependency(string key)
        {
            if (GetCache(key) == null)
            {
                var strRes = new System.IO.StreamReader(fileName).ReadToEnd();
                SetCacheByCacheDependency(key, strRes);
            }
            return GetCache(key);
        }

        /// <summary>
        ///设置数据库缓存依赖（需要配置服务项）
        /// </summary>
        /// <param name="key"></param>
        /// <param name="value"></param>
        /// <returns></returns>
        public static void SetCacheBySqlCacheDependency(string key,object value)
        {
            var cache = HttpRuntime.Cache;
            cache.Insert(key, value, new SqlCacheDependency("test", "user"));
        }

        /// <summary>
        /// 获取数据库缓存依赖
        /// </summary>
        /// <param name="key"></param>
        /// <returns></returns>
        public static object GetCacheBySqlCacheDependency(string key)
        {
            if (GetCache(key) == null)
            {
                var value = GetList();
                SetCacheBySqlCacheDependency(key, value);
            }
            return GetCache(key);
        }

        public static List<User> GetList()
        {
            using (SqlConnection conn=new SqlConnection("data source=.;initial catalog=test;user id=sa;password=123"))
            {
                using (SqlDataAdapter adapter = new SqlDataAdapter("select Id,Name,Age,Password from [user]", conn))
                {
                    var ds=new DataSet();
                    if(conn.State == ConnectionState.Closed) conn.Open();
                    adapter.Fill(ds, "myds");
                    var dt = ds.Tables[0];
                    return DataTableToList<User>(dt);
                }
            }
        }

        public static List<T> DataTableToList<T>(DataTable dt)
        {
            List<T> list = default(List<T>);
            if (dt != null && dt.Rows.Count > 0)
            {
                list = new List<T>();
                System.Reflection.PropertyInfo[] propertyInfos = typeof(T).GetProperties();
                foreach (DataRow dr in dt.Rows)
                {
                    T t = Activator.CreateInstance<T>();
                    foreach (var pro in propertyInfos)
                    {
                        if (pro.CanWrite && dt.Columns.Contains(pro.Name)) pro.SetValue(t, dr[pro.Name], null);
                    }
                    list.Add(t);
                }
            }
            return list;
        }
   }