[置顶]【收集】Linq 查询方法收集

开始不间断收集linq查询使用的方法，日拱一卒，月可渡江。

查询排序取前6个 var newshops = storeDB.Shops.OrderByDescending(a => a.JoinDate).Take(6).ToList(); 查询列表 常用用法 var order = (from u in storeDB.Orders where u.OrderId == id select u).ToList(); Find () foreach (OrderDetail od in order_detail) { var dish = storeDB.Dishs.Find(od.DishId); } First() var b = (from a in storeDB.Orders select a).First(x => x.OrderId.Equals(id));

Any()

用于判断集合中是否有元素满足某一条件；不延迟。（若条件为空，则集合只要不为空就返回True，否则为False）。 bool isValid = storeDB.Orders.Any(o => o.OrderId == id && o.Username == User.Identity.Name); Take(int n); var shops = (from u in storeDB.Shops where u.TitleShopValue > 0 orderby u.TitleShopValue descending select u).Take(8).ToList();

取排前面的N个。

Contains();提供模糊查询 var shops = (from u in DB.Shops where u.Name.Contains(searchKey) orderby u.TitleShopValue descending select u).ToList(); var id =storeDB.Users.SingleOrDefault(u => u.UserName ==model.UserName).UserID;

 

判断，返回bool类型 return (from s in roles from userrole in userroles where s.Equals(userrole) select s).Any(); 条件查询 IList<UserFollow> Follows = db.UserFollows.Where(o => o.UserId == userid).ToList(); 统计计数 var ageCoun = (from s in GetStudents() select s.Age).Count(a=>a>22);

 

Var Count = LDB.User.Count(o=>o.age == 23);