【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。

1. 查询排序取前6个

   var newshops = storeDB.Shops.OrderByDescending(a => a.JoinDate).Take(6).ToList();

2. 查询列表 常用用法
   

   var order = (from u in storeDB.Orders
                where u.OrderId == id
                select u).ToList();

3. Find ()
   

   foreach (OrderDetail od in order_detail)
   {                                       
   var dish = storeDB.Dishs.Find(od.DishId);
   }

4. First()
   

   var b = (from a in storeDB.Orders
            select a).First(x => x.OrderId.Equals(id));

5. 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); 

6. 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。

7. 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();

8. var id =storeDB.Users.SingleOrDefault(u => u.UserName ==model.UserName).UserID;

    

9. 判断，返回bool类型
   

   return (from s in roles from userrole in userroles where s.Equals(userrole) select s).Any();
   

10. 条件查询
    

    IList<UserFollow> Follows = db.UserFollows.Where(o => o.UserId == userid).ToList();
    

11. 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);
    

     

13.