C# EF Code first One To Many Models

Question

I have a DB that looks like this:

 Houses
    - HouseId
 Rooms
    - RoomId

 HouseRooms
    - HouseRoomId
    - HouseId
    - RoomId

class House
{
   [Key]
   public virtual int HouseId{ get; set; }


   public DbSet<HouseRoom> Rooms{ get; set; }
 }    

class HouseRoom

{ [Key] public virtual int HouseRoomId{ get; set; }

   public virtual int HouseId{ get; set; }
   public virtual int RoomId{ get; set; }

   [ForeignKey("RoomId")]
   Public Role RoomInfo {get; set;}
}

class Room
{ 
   [Key] 
   public virtual int RoomId {get; set;}

   public string RoomName {get; set;}
}

I just need the House entity/mode to load all the rooms records. Noticed that the JOIN table has a PK name HouseRoomId but this is not the key that need to match the key in House. House.HouseId need to match HouseRoom.HouseId.

How can I get this to work?

Just out of curiosity, why/how can a Room be in more than 1 House? — Alastair Pitts
– Alastair Pitts, Commented Jun 4, 2013 at 0:41
it is a RoomType really like Kitchen, BED 1 etc for example,, each house has a floorplan and each floor plan has similar roomtypes. The example is just to get an idea how to get one to many working in code first. — Arcadian
– Arcadian, Commented Jun 4, 2013 at 0:43
Ah, so it's more of a Room template, rather than a room itself, I understand :) — Alastair Pitts
– Alastair Pitts, Commented Jun 4, 2013 at 0:58

Community · Accepted Answer · 2017-05-23 12:28:57Z

2

Ok first this is a many-to-many, not one-to-many. Second, you need to set the relationship on ModelCreation to let the DbContext know about this relationship. Also, you need to make your List<Room> virtual to enable it to load when you need it. Please look at this example. Code First Entity Framework Many-to-Many relationships

Also, for the record, you do not need to specify [key], it is already there for you by default

edited May 23, 2017 at 12:28

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answered Jun 4, 2013 at 1:20

Has AlTaiar

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1 Comment

Arcadian Over a year ago

The virual did it. I know it was a many to many but I wasnt able to get the one to many loaded. I think I have it now. Thanks. Still dont know how it knows how to map the relationships..

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