Question

Please take a look at following code:

public class SomeEntity
{
    public int Id { get; set; }

    public int UserId { get; set; }
    public virtual User User { get; set; }
}

public class SomeEntityA : SomeEntity
{
    public int Number { get; set; }
}

public class SomeEntityB : SomeEntity
{
    public string Text { get; set; }
}

public class User
{
    public int Id { get; set; }
    public int Username { get; set; }

    public virtual ICollection<SomeEntityA> SomeEntitiesA { get; set; }
    public virtual ICollection<SomeEntityB> SomeEntitiesB { get; set; }
}

My question is – is there a way to set the FluentApi to make relationships shown above work properly? Currently when new SomeEntityA object is being added to User, EF creates a new record in SomeEntities table with properly set User_Id FK, however in SomeEntitesA which is an inherited table, there’s also a FK property User_Id – set as null and when I try to get SomeEntitesA collection from User object – it’s empty. I do realize why that happens, but I’m not sure whether there’s a way to fix this? The only solution that comes to my mind at this moment is to replace following code:

    public virtual ICollection<SomeEntityA> SomeEntitiesA { get; set; }
    public virtual ICollection<SomeEntityB> SomeEntitiesB { get; set; }

with:

    public virtual ICollection<SomeEntity> SomeEntitiesA { get; set; }
    public virtual ICollection<SomeEntity> SomeEntitiesB { get; set; }

and configure FluentApi.

Any thoughts would be highly appreciated.

Answer 1

Have a look at this question/answer, the classes have exactly the same structure as yours and there is a detailed explanation why things are not working as expected:

Is inheritance of navigation properties supported?

As Slauma pointed out, there is a rather simple solution to get around this by doing the following (copied from the linked answer and fit to your example):

public class User
{
    public int Id { get; set; }
    public int Username { get; set; }

    // this is necessary to have access to the related SomeEntityAs/SomeEntityBs
    // also it cant be private otherwise EF will not overload it properly
    public virtual ICollection<SomeEntity> SomeEntities { get; set; }

    public IEnumerable<SomeEntityA> SomeEntitiesA { get { return this.SomeEntities.OfType<SomeEntityA>(); } }
    public IEnumerable<SomeEntityB> SomeEntitiesB { get { return this.SomeEntities.OfType<SomeEntityA>(); } }
}