/// <summary>        /// 是否为NULL或者空        /// </summary>        /// <param name="str"></param>        /// <returns></returns>        public static bool IsNullOrEmpty(this string str)        {            if (str == null || str.Trim() == "")            {                return true;            }            return false;        }

using System;using System.Collections.Generic;using JChen.Ext;namespace JChen.Caching{    /// <summary>    /// 缓存    /// </summary>    /// <typeparam name="T"></typeparam>    public class Cache<T>    {        /// <summary>        /// 锁        /// </summary>        private static object lockObj = new object();        /// <summary>        /// 默认Cache        /// </summary>        private static Cache<T> _default = new Cache<T>(true);        /// <summary>        /// 每个实例的缓存        /// </summary>        private Dictionary<string, T> instanceCache = null;        /// <summary>        /// 默认的缓存        /// </summary>        private static Dictionary<string, T> defaultCache = new Dictionary<string, T>();        /// <summary>        /// 缓存        /// </summary>        public Cache()        {            instanceCache = new Dictionary<string, T>();        }        /// <summary>        /// 私有构造,区别于Cache(),只是为了实例化_default;        /// 对于默认的缓存,不需要且不能实例化instanceCache        /// </summary>        /// <param name="isDefualt"></param>        private Cache(bool isDefualt)        {        }        /// <summary>        /// 相对于T的默认缓存实例        /// 特别注意:对于相同的类型T,Default是同一个对象        /// </summary>        public static Cache<T> Default { get { return _default; } }        /// <summary>        /// 设置或获取缓存数据        /// </summary>        /// <param name="key">键,不能为空</param>        /// <returns>如果键为空,返回值为类型T的默认值</returns>        public T this[string key]        {            get            {                if (instanceCache != null)                {                    if (instanceCache.ContainsKey(key))                    {                        return instanceCache[key];                    }                }                else                {                    if (defaultCache.ContainsKey(key))                    {                        return defaultCache[key];                    }                }                return default(T);            }            set            {                if (key.IsNullOrEmpty())                {                    throw new ArgumentNullException("key", "键不能为空!");                }                if (instanceCache != null)                {                    if (instanceCache.ContainsKey(key))                    {                        instanceCache[key] = value;                    }                    else                    {                        lock (lockObj)                        {                            instanceCache.Add(key, value);                        }                    }                }                else                {                    if (defaultCache.ContainsKey(key))                    {                        defaultCache[key] = value;                    }                    else                    {                        lock (lockObj)                        {                            defaultCache.Add(key, value);                        }                    }                }            }        }        /// <summary>        /// 缓存数量        /// </summary>        public int Count        {            get            {                if (instanceCache != null)                {                    return instanceCache.Count;                }                else                {                    return defaultCache.Count;                }            }        }        /// <summary>        /// 移除指定键的缓存值        /// </summary>        /// <param name="key">键,不能为空</param>        /// <returns></returns>        public bool Remove(string key)        {            if (key.IsNullOrEmpty())            {                return false;            }            if (instanceCache != null)            {                if (instanceCache.ContainsKey(key))                {                    return instanceCache.Remove(key);                }            }            else            {                if (defaultCache.ContainsKey(key))                {                    return defaultCache.Remove(key);                }            }            return false;        }        /// <summary>        /// 清空缓存        /// </summary>        public void Clear()        {            if (instanceCache != null)            {                instanceCache.Clear();            }            else            {                defaultCache.Clear();            }        }    }}