private static List<Menu> MenuTree()

        {

            var menu1 = new Menu { Id = , ParentId = , Name = "aaa" };

            var menu2 = new Menu { Id = , ParentId = , Name = "bbb" };

            var menu3 = new Menu { Id = , ParentId = , Name = "ccc" };

            var menu4 = new Menu { Id = , ParentId = , Name = "ddd" };

            var menu5 = new Menu { Id = , ParentId = , Name = "eee" };

            var menu6 = new Menu { Id = , ParentId = , Name = "fff" };

            var menu7 = new Menu { Id = , ParentId = , Name = "ggg" };

            var menu8 = new Menu { Id = , ParentId = , Name = "hhh" };

            var menuAll = new List<Menu> { menu1, menu2, menu3, menu4, menu5, menu6, menu7, menu8 };

            var menuList = new List<Menu> { menu1, menu2, menu3, menu4, menu5, menu7, menu8 };

          //第一种方法

            while (true)

            {

                var idList = menuList.Select(x => x.Id).ToList();

                idList.AddRange(menuList.Select(x => x.ParentId).ToList());

                idList = idList.Distinct().ToList();

                var menus = menuAll.Where(x => idList.Contains(x.Id)).ToList();

                if (menus.Count != menuList.Count)

                {

                    menuList = menus;

                    continue;

                }

                break;

            }

　　　　　　　//第二种方法　

            var ret = new List<Menu>();

            foreach (var menu in menuList)

            {

                var model = menuList.FirstOrDefault(x => x.Id == menu.ParentId);

                if (model == null)

                {

                    ret.Add(menu);

                    continue;

                }

                model.Children.Add(menu);

            }

            return ret;

        }