有关目录树的操作

        /// <summary>        /// 取得所有子分类ID        /// </summary>        /// <param name="categoryid">要取得的根分类ID</param>        /// <param name="result">结果列表</param>        public static void GetAllSubCatIds(int categoryid, List<int> result)        {            foreach (category item in category.Find(c => c.parentid == categoryid))            {                result.Add(item.id);                GetAllSubCatIds(item.id, result);            }        }

        //查出category中所有的父节点        public static List<ECategory> getNavList(int categoryid)        {            List<ECategory> navList = new List<ECategory>();            category cate1 = category.SingleOrDefault(p => p.id == categoryid);            int parentid = cate1.parentid;            int cid = cate1.id;            while (parentid >= 0)            {                category cate = category.SingleOrDefault(p => p.id == cid);                ECategory model = new ECategory();                model.id = cate.id;                model.name = cate.name;                model.orderid = cate.orderid;                model.parentid = parentid;                navList.Add(model);                if (parentid != 0)                {                    category cate2 = category.SingleOrDefault(p => p.id == cate.parentid);                    parentid = cate2.parentid;                    cid = cate.parentid;                }                else                    break;            }            navList.Reverse();            return navList;        }

 //如果是article页面，获得他父节点在category中的id        public static int getid(int id)        {            article article = article.SingleOrDefault(p => p.id == id);            int categoryid = article.categoryid;            return categoryid;        }        //找到所在id的order==2父节点        public static int getfather(int id)        {            category category1 = category.SingleOrDefault(p => p.id == id);            int order = category1.orderid;            int parent = category1.parentid;            int fatherid = id;            while (order >= 2)            {                category categ = category.SingleOrDefault(p => p.id == parent);                order = categ.orderid;                parent = categ.parentid;                fatherid = categ.id;            }            return fatherid;        }        //获得当前id的1级导航        public static int getfirst(int id)        {            category categ = category.SingleOrDefault(p => p.id == id);            int firstid = id;            if (categ.orderid != 1)            {                firstid = getfather(id);                category cate = category.SingleOrDefault(p => p.id == firstid);                if (cate.orderid != 1)                { firstid = cate.parentid; }            }            return firstid;        }