Self-referencing many-to-many relationship EF code first

Question

I work with ASP.NET MVC With Durandal/Breeze templates.

Let's say I have the following class:

public class Person
{
    public int Id { get; set; }
    public string Firstname { get; set; }    
    public string Lastname { get; set; }
    public virtual List<Person> Friends { get; set; }
}

With the following EF Fluent API:

modelBuilder.Entity<Person>()
            .HasMany(m => m.Friends)
            .WithMany()
            .Map(m => m.ToTable("Friends"));

The database is generated successfully.

The problem is when I perform a que

ry with Breeze (client side) I have no data for the Friends property.

    var query = entityQuery.from('Person')
        .where('id', '==', 123)
        .expand("Friends");

When the query is executed I get as result the requested People entity with all the data except the Friends property is always an empty array. When I check the Json answer I see that also the data are transmitted. Even data for the Friends property. However they are not linked to the Friends property itself.

My question: what do I have to do to have my Friends property filled with values?

Thanks.

sbelini · Accepted Answer · 2013-08-20T17:16:47.110

You must declare a foreign key in Person. Breeze requires the FK to correctly resolve associations.

Edit:

I just realized you are asking about a many-to-many relationship. (yeah, I should have read the post title...) Breeze does not support many-to-many associations. However, you could have two one-to-many relationships to work as a many-to-many. (i.e. many-to-one-to-many) In this case, you will need to define the linking table/entity and the foreign key as mentioned earlier. (see http://www.breezejs.com/documentation/navigation-properties)

score 1 · Answer 2 · edited May 23 '17 at 12:15

1

Try this answer: *Note that this is incomplete because i do not see the other table that you are trying to m-2-m with Persons. ( You will only want to use Persons Table and the 2nd Table , NOT table=Friends.

 db.Person
          .Include(c => c.Friends)
          .Where(c => c.Friends.Any(up => up.FriendVlaue == c.FirstName)) //c.from Persons
          .Select(c => new
          {
              PersonID = c.ID,
              PersonName = c.FirstName,
              PersonCount = c.Person.Count()
          })

         {

From This answer

edited May 23 '17 at 12:15

Community

1
1

answered Aug 20 '13 at 16:09

Don Thomas Boyle

3,055
3
32
54

My apologies, this is how to retrieve related data not how to insert. – Don Thomas Boyle Aug 20 '13 at 16:12

score 0 · Answer 3 · answered Aug 20 '13 at 14:26

0

You should include Friends in the results. You can do this by adding Include("Friends")at Server Side API.

[HttpGet]
public IQueryable<Person> Persons()
{
   return _contextProvider.Persons.Include("Friends");
}

If you don't want to return always the Friendsreference, you can create another method in the API such as PersonsWithFriends as suggested in here (Specialized query actions).

answered Aug 20 '13 at 14:26

margabit

2,924
18
24

I tried as you suggested but I still cannot find any data in my Friends property. When I place a breakpoint in my returned statement in my Controller `return _contextProvider.Persons.Include("Friends");` I see my Friends property populated but in my breeze querry I don't see any data for this Friends property. There must be something special to do related to breeze... Thanks anyway. – Bronzato Aug 20 '13 at 14:42
Can you include your breeze query in JS? I have impemented this before with the same scenario as yours and it works fine. – margabit Aug 20 '13 at 14:47
My breeze querry (in JS) is already showed in my question, thanks for your help. – Bronzato Aug 20 '13 at 14:52
Can you try to remove the expand("Friends"); ?? – margabit Aug 20 '13 at 15:08
:( http://durandalspa.codeplex.com/ in this project I used Durandal and Breeze and there's the same scenario with Order and OrderLines. Take a look, maybe it helps.. Good luck! – margabit Aug 20 '13 at 15:14

Self-referencing many-to-many relationship EF code first

3 Answers3

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