CODEWITHSUNDEEP
c#entity-framework-core
Hani Safa
Hani Safa

Reputation: 101

Many-to-many with TPC inheritance in EF Core

I'm having a trouble configuring May-to-many with TPC inheritance

public class TestB
{
    public int Id { get; set; }
    public string Name { get; set; }
    public ICollection<ParentClass> ParentClasss { get; set; }
}

public abstract class ParentClass
{
    public int Id { get; set; }
    public string Name { get; set; }
    public ICollection<TestB> TestBs { get; set; }
}

[Table("Child_A")]
public class Child_A: ParentClass
{
    public string childAName { get; set; }
}

[Table("Child_B")]
public class Child_B: ParentClass
{   
    public string childbName { get; set; }
}

the many to many relation is on the abstract class, the generated tables are

TestB

ParentClass

ParentClassTestB : the many to many relation

Child_A : have FK for the ParentClass

Child_B : have FK for the ParentClass

what I need is to have the many to many directly with Child_A and Child_B.

so the generated tables will be something like

TestB

Child_A

Child_ATestB : the many to many relation table between Child_A and TestB

Child_B

Child_BTestB : the many to many relation table between Child_B and TestB

regards

Upvotes: 0

Views: 448

Answers (1)

David Browne - Microsoft
David Browne - Microsoft

Reputation: 88852

what i need is to have the many to many directly with Child_A and Child_B.

Then don't map ParentClass as an Entity. You can still have it as the parent class in your code, but as far as the database is concerned Clild_A and Child_B are unrelated.

This is especially important in TPH, which has serious performance implications. This way there's simply no database overhead for your inheritance hierarchy. And the only real downside is that you don't have a built-in search over all ParentClass entities.

The only change is that if you don't want ParentClass involved in the M2M in the database, you can't have a navigation property from TestB to ParentClass. So

public class TestB
{
    public int Id { get; set; }
    public string Name { get; set; }
    public ICollection<Child_A> ParentClasssA { get; set; }
    public ICollection<Child_B> ParentClasssB { get; set; }
}

public abstract class ParentClass
{
    public int Id { get; set; }
    public string Name { get; set; }
    public ICollection<TestB> TestBs { get; set; }
}

[Table("Child_A")]
public class Child_A : ParentClass
{
    public string childAName { get; set; }
}

[Table("Child_B")]
public class Child_B : ParentClass
{
    public string childbName { get; set; }
}

Upvotes: 1

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