缓存篇(Cache)~第一回 使用static静态成员实现服务器端缓存(导航面包屑)

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今天写缓存篇的第一篇文章，在写完目录后，得到了一些朋友的关注，这给我之后的写作带来了无穷的力量，在这里，感谢那几位伙伴，哈哈！

书归正传，今天我带来一个Static静态成员的缓存，其实它也不是什么缓存，就是Ｃ#语言里的一个特性，静态成员在被初始化后它将不会再被执行，即，他里面的内容只会被执行一次，直到你的网站被重启后（只考虑在单线程情况下）。相信大家都在做网站时，遇到了网站导航面包屑功能点吧，一般，我们把它写死在页面上，这种作法没有任何可扩展性和可维护性，所以，今天我们要改善一下这个功能点，使用的技术就是静态成员缓存和树型结构。

先看一下导航的结构

　　 /// <summary>
    /// 导航面包
    /// </summary>
    public class BannerBread
    {
        public string DisplayTitle { get; set; }
        public string Url { get; set; }
        public int ID { get; set; }
        public int ParentID { get; set; }
        public BannerBread Parent { get; set; }
    }

下面这段代码就是实现导航的核心，它对外提供一个唯一的访问点，所以，和两个公开的方法，一个是GetBanner，用来返回当前URL对应的导航完整对象（包括祖宗对象），GenerateStandardBanner方法返回一个标准的导航，当前，具体的项目，你可以自己

去实现它。

    /// <summary>
    /// 导航生产类
    /// </summary>
    public static class BannerBreadFactory
    {
        /// <summary>
        /// BannerBread单例实例对象
        /// </summary>
        static readonly List<BannerBread> Instance = new List<BannerBread>();

        static BannerBreadFactory()
        {
            Instance.Add(new BannerBread { ID = , DisplayTitle = "首页", Parent = null, ParentID = , Url = "/" });
            Instance.Add(new BannerBread { ID = , DisplayTitle = "关于我们", Parent = null, ParentID = , Url = "/Home/About" });
            Instance.Add(new BannerBread { ID = , DisplayTitle = "联系我们", Parent = null, ParentID = , Url = "/Home/Contact" });
        }
        /// <summary>
        /// 得到当前URL的祖宗节点
        /// </summary>
        /// <param name="url"></param>
        /// <returns></returns>
        public static BannerBread GetBanner(string url)
        {
            var entity = Instance.FirstOrDefault(i => i.Url.ToUpper() == url.ToUpper());
            GetFather(entity);
            return entity;
        }
        /// <summary>
        /// 标准的导航，程序开发人员可以根据自己的需要，在具体项目中去定义它
        /// </summary>
        /// <param name="url"></param>
        /// <returns></returns>
        public static string GenerateStandardBanner(string url)
        {
            var entity = GetBanner(url);
            StringBuilder str = new StringBuilder();
            while (entity != null)
            {
                str.Insert(, "/<span><a href='" + entity.Url + "'>" + entity.DisplayTitle + "</a></span>");
                entity = entity.Parent;
            }
            return str.ToString().StartsWith("/") ? str.ToString().Substring() : "未找到导航项";
        }
        /// <summary>
        /// 得到祖宗
        /// </summary>
        /// <param name="son"></param>
        private static void GetFather(BannerBread son)
        {
            if (son != null)
            {
                son.Parent = Instance.FirstOrDefault(i => i.ID == son.ParentID);
                GetFather(son.Parent);
            }
        }

    }

上面的代码中，对于导航数据的部分，我选择了静态数据，当然，真实的项目中，需要将这块放到数据库里，以便于后期维护，一般地，我们可以在布局页去调用它来实现导航显示的功能，非常方便，下面是运行后的效果截图

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" 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对于具体的显示，我们的前台显示可以自己去组装，上面显示的只是一种标准的形式，即由GenerateStandardBanner方法提供的形式。

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