Question

My Model looks like like this

public class User
{
    public int ID { get; set; }

    public string Name { get; set; }


    /*Users who are following current user*/
    public virtual ICollection<User> Followers { get; set; }

    /*Users whom current user is following*/
    public virtual ICollection<User> Following { get; set; }


    /*current user has ignored these users*/
    public virtual ICollection<User> Ignores { get; set; }

}

To add data

        User john = new User { Name = "john" };
        User mary = new User { Name = "mary" };
        User david = new User { Name = "david" };

        john.Following = new List<User> { mary };
        mary.Followers = new List<User> { john};
        john.Ignores = new List<User> { david};

        context.Users.Add(john);
        context.Users.Add(mary);
        context.Users.Add(david);

        context.SaveChanges();

Doing this is giving error:

Unable to determine a valid ordering for dependent operations. Dependencies may exist due to foreign key constraints, model requirements, or store-generated values.

If i remove the propert Ignores from User Model its working perfect, but with ignores it doesn’t.

I think there is some mapping thats need to be done, please suggest me how can i do this!!

Answer 1

The problem seems to be that EF does not know which two are a many-to-many and which one is a one-to-many. You could try explicitly stating these rather than relying on convention. Try overriding the OnModelCreating(DbModelBuilder) method of the DbContext class (if you are using DbContext).

protected override void OnModelCreating(DbModelBuilder mb)
{
    mb.Entity<User>()
        .HasMany(u => u.Ignores)
        .WithReequired()
        .HasForeignKey(u => u.ID);

    mb.Entity<User>()
        .HasMany(u => u.Followers)
        .WithMany(u => u.Following);
        // If you want to specify a table, use the following line:
        // .Map(m => m.ToTable("CustomManyToManyTableName");
}

Notice: I made this up off the top of my head so don’t rely on my syntax and such precisely, but it should be pretty close.