c# - 查询 Linq 加入多对多

Question

我正在为我的 MVC2 应用程序使用 Linq-SQL 实体。

我有那些表/实体

Person ( ID , Name , Surname ) Car (ID , Model , Name) Reseller ( ID , Name)

我有那 2 个多对多表

Persons_Cars ( ID , ID_Person , ID_CAR) Persons_Resellers ( ID, ID_Person, ID_Reseller)

 public MyModel {

   //Some Fields

    public List<CarPerson> carList;

    public CarPerson 
    {
      String detail;
      int id;
    }
}
 var query=(from person in data.Person

                     join PerCar in data.Persons_Cars on person.ID equals Persons_Cars.ID_Person into JoinedPerCar
                     from PerCar in JoinedPerCar.DefaultIfEmpty()

                     join car in data.car on PerCar .id_car equals car.ID into JoinedCarPe
rson
                     from car in JoinedCarPerson.DefaultIfEmpty()

                     join PerReseller in data.Persons_Resellers on person.ID equals  PerReseller .id_person into JoinedPersReseller 
                     from PerReseller in JoinedPersReseller.DefaultIfEmpty()

                     join Reseller in data.Reseller on PerReseller.id_reseller equals Reseller.ID into JoinedResellerPers
                     from Resller in JoinedFormazioneComp.DefaultIfEmpty()

                     where person.ID_USER == USER.ID 
                     select new MyModel
                                { 
                                     carList = JoinedPerCar.Select(m=>new CarPerson {detail=m.car.Model,id = m.ID}).ToList()},
                                //Other
                                });

我知道这是完全错误的，但我是 Linq-SQL 的新手我现在有一个问题:

查询有效，但我的结果是错误的。事实上，如果一个人有 2 辆车，我会两次收到同一个人的 2 辆汽车 list 。

例子

布朗先生有 2 辆车我收到布朗先生 ---> 汽车 list (Car1，Car2)Mr Brown ---> 汽车 list (Car1, Car2)

所以我需要如果一个人有 2 辆车，我只得到 1 个拥有自己汽车的人的结果

有没有办法更好地编写此查询？如何解决我的问题？

谢谢

Answer 1

我认为简单的子查询就可以完成这项工作(对于经销商也是如此):

from p in data.Person
select new MyModel {
  carList = (from pc in data.Persons_Cars
             join c in data.car on pc.id_car equals c.ID
             where pc.ID_Person == p.ID 
             select c).ToList()
};

如果您定义了导航属性，那么查询会更加简单(Linq 会为您做连接):

from p in data.Person
select new MyModel {
   carList = p.Person_Cars.Select(pc => pc.Car).ToList()
};