/// <summary>

    /// 缓存帮助类

    /// </summary>

    public class CacheHelper

    {

        /// <summary>

        /// 创建缓存项的文件

        /// </summary>

        /// <param name="key">缓存Key</param>

        /// <param name="obj">object对象</param>

        public static void Insert(string key, object obj)

        {

            //创建缓存

            HttpContext.Current.Cache.Insert(key, obj);

        }

        /// <summary>

        /// 移除缓存项的文件

        /// </summary>

        /// <param name="key">缓存Key</param>

        public static void Remove(string key)

        {

            //创建缓存

            HttpContext.Current.Cache.Remove(key);

        }

        /// <summary>

        /// 创建缓存项的文件依赖

        /// </summary>

        /// <param name="key">缓存Key</param>

        /// <param name="obj">object对象</param>

        /// <param name="fileName">文件绝对路径</param>

        public static void Insert(string key, object obj, string fileName)

        {

            //创建缓存依赖项

            CacheDependency dep = new CacheDependency(fileName);

            //创建缓存

            HttpContext.Current.Cache.Insert(key, obj, dep);

        }

        /// <summary>

        /// 创建缓存项过期

        /// </summary>

        /// <param name="key">缓存Key</param>

        /// <param name="obj">object对象</param>

        /// <param name="expires">过期时间(分钟)</param>

        public static void Insert(string key, object obj, int expires)

        {

            HttpContext.Current.Cache.Insert(key, obj, null, Cache.NoAbsoluteExpiration, new TimeSpan(, expires, ));

        }

        /// <summary>

        /// 获取缓存对象

        /// </summary>

        /// <param name="key">缓存Key</param>

        /// <returns>object对象</returns>

        public static object Get(string key)

        {

            if (string.IsNullOrEmpty(key))

            {

                return null;

            }

            return HttpContext.Current.Cache.Get(key);

        }

        /// <summary>

        /// 获取缓存对象

        /// </summary>

        /// <typeparam name="T">T对象</typeparam>

        /// <param name="key">缓存Key</param>

        /// <returns></returns>

        public static T Get<T>(string key)

        {

            object obj = Get(key);

            return obj == null ? default(T) : (T)obj;

        }

    }

var _cache = CacheHelper.Get<User>(key);

if (_cache == null)

{

        CacheHelper.Insert(key,obj,);//存入续存，30分钟

        _cache = CacheHelper.Get<User>(key);

}

return _cache;