我需要定义这两个实体之间的任何关系吗？

Question

Hello everyone and sorry for this noob question. I'm currently developing an ASP.NET Core 3.1 WebAPI for a Travel Planner & Assistant web application. I am using EF Core and Identity.

My model consists of the following classes:

Vacation , Reservation , Hotel , Room , Review , a custom IdentityUser and Record , UserRecord for a better management of the creation and modification date and user.

Each Vacation has a List<Reservation> ; each Hotel has a List<Room> and a List<Review> .

My question is, should I define any relationship between Reservation and Room ?

I'm thinking each Reservation should know which Room is going to book, so it seems logical to have the Room inside. But that instance of Room already exists in the List<Room> of the Hotel .

Answer 1

I'm thinking each Reservation should know which Room is going to book, so it seems logical to have the Room inside. But that instance of Room already exists in the List of the Hotel.

What you tought is totally correct. You don't need to add a collection naivgational property of type Reservation (eg List<Reservation> ) into your Room entity.

By adding a Room navigational property on Reservation entity, EF Core can handle the remainging things and by applying default convention it will consider that a reservation is for one room and a room can be related to multiple reservations even you don't created the reservation type into the Room entity.

Answer 2

What I think, you should have a new entity HotelRoom, which contains Hotel and Room, many to many relation between Hotel and Room. Then for every Reservation you should have Hotel and a list of HotelRoom in it.

public class Hotel
{
    public int Id { get; set; }
    public string Name { get; set; }
}
public class Room
{
    public int Id { get; set; }
    public int RoomNumber { get; set; }
}
public class HotelRoom
{
    public int HotelId { get; set; }
    public Hotel Hotel { get; set; }
    public int RoomId { get; set; }
    public Room Room { get; set; }
}

public class Reservation
{
    public int Id { get; set; }
    public int HotelId { get; set; }
    public Hotel Hotel { get; set; }
    public List<HotelRoom> HotelRooms { get; set; }
}