Dictionary实现的缓存类Cache

        /// <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();
            }
        }
    }
}