EF数据库迁移命令 C#无限极递归树及三元运算符简写

1、EF数据库迁移控制台命令：

Enable-Migrations
Add-Migration init
update-database

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2、C#三元运算符简写

is_seckill_activity ？is_seckill_activity  ：false
is_seckill_activity ?? false

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3、C#无限极递归树

public JsonResult GetTreeMenuList()
        {
            var menuTreeList = authService.GetTreeMenuList(-1);
            var treeList = new List<TreeListViewModel>();
            foreach (var item in menuTreeList)
            {
                var temp = new TreeListViewModel()
                {
                    id = item.id,
                    text = item.name,
                    pid = item.pid
                };
                treeList.Add(temp);
            }
            var treeItem = new TreeListViewModel()
            {
                id = 0,
                text = "跟节点",
                nodes = new List<TreeListViewModel>()
            };
            var result = BuildTreeList(treeList, treeItem);
            return Json(result, JsonRequestBehavior.AllowGet);
        }

        private TreeListViewModel BuildTreeList(List<TreeListViewModel> all, TreeListViewModel curItem)
        {
            var subItems = all.Where(m => m.pid == curItem.id).ToList();
            curItem.nodes = new List<TreeListViewModel>();
            curItem.nodes.AddRange(subItems);
            foreach (var subItem in subItems)
            {
                BuildTreeList(all, subItem);
            }
            return curItem;
        }