Entity Framework Many To Many with TPT Approach

Question

What I try to reach is an NM relationship between AbstractUser and Plant in use with TPT inheritance.

enter image description here

When I try to configure the relationship,

modelBuilder.Entity<Plant>().HasMany(c => c.RemindedByUsers).WithMany().Map(m =>
{
    m.ToTable("UserHasRemindedPlant");
});

I get the following exeption:

Additional information: Introducing FOREIGN KEY constraint 'FK_dbo.UserHasRemindedPlant_dbo.AbstractUsers_AbstractUser_Id' on table 'UserHasRemindedPlant' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.

How do I set the ON DELETE or ON UPDATE action on many to many releationships on tpt abstract entities?

When I use the line above everything works fine but I need this convention for other entities.

modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();

Here my entity classes:

AbstractUser

public abstract class AbstractUser
{
    protected AbstractUser()
    {
        RemindedPlants = new Collection<Plant>();
    }

    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }

    ...


    [Required]
    public SchoolYear SchoolYear { get; set; }

    public virtual ICollection<Plant> RemindedPlants { get; private set; }
}

Studend

[Table("Student")]
public class Student : AbstractUser
{
    //some unrelevant props here

}

Teacher

[Table("Teacher")]

public class Teacher : AbstractUser
{
    //some unrelevant props here

}

The problem is somewhere else. If it works when removing the `OneToManyCascadeDeleteConvention` the problem can't be the many-to-many relationship. Does for example the `Plant` have a (required) reference to a user (AbstractUser or one of the derived users)? This would indeed cause multiple delete paths from the `AbstractUser` table to the `UserHasRemindedPlant` table and throw the exception. — Slauma, Apr 18 '14 at 17:05

score 1 · Answer 1 · answered Apr 16 '14 at 14:12

1

You must disable cascading delete with Fluent API .WillCascadeOnDelete(false):

modelBuilder.Entity<Plant>().HasMany(c => c.RemindedByUsers).WithMany().WillCascadeOnDelete(false).Map(m =>{
m.ToTable("UserHasRemindedPlant");});

answered Apr 16 '14 at 14:12

Abolfazl Hosnoddin

126
6

Thanks for your reply. For some reason, visual studio cannot resolve WillCascadeOnDelete(false) after WithMany(). Has this changed after EF6? – Nando Apr 16 '14 at 14:57
Which version of EF are you using? – Abolfazl Hosnoddin Apr 16 '14 at 15:13
EF: 6.0.2 Dot.Net: 4.5 – Nando Apr 16 '14 at 15:17
Then you should have no problems in using WillCascadeOnDelete(false). what do you get on AutoComplete after WithMany()? – Abolfazl Hosnoddin Apr 16 '14 at 15:20
GetType, Map, MapToStoredProcedures. If I choose WithOptional or WithRequired "WillCascadeOnDelete" is available, but not after WithMany :/ – Nando Apr 16 '14 at 15:24
I did not notice WithRequired is needed to call WillCascadeOnDelete. – Abolfazl Hosnoddin Apr 16 '14 at 15:41
So there is no possible way to solve this? Maybe overwriting OneToManyCascadeDeleteConvention and skip these two entities? Or disable the convention globaly and enable it if needed? – Nando Apr 16 '14 at 15:47

score 0 · Answer 2 · edited May 23 '17 at 10:26

0

Try this:

modelBuilder.Conventions.Remove();

see: https://stackoverflow.com/a/13705637/491181

edited May 23 '17 at 10:26

Community

1
1

answered Apr 24 '14 at 13:35

ridermansb

10,779
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115
226

Entity Framework Many To Many with TPT Approach

2 Answers2