实体框架代码优先，与继承的1：1关联

Question

I have an abstract class UserProfile , it has a subclass Tenant , so the relationship is 1:1 - one 'user' is one 'tenant'.

Is this the correct way to implement table-per-type inheritance, on a 1:1 basis?

[Table("UserProfile")]
public abstract class UserProfile
{
    [Key]
    [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
    public int UserId { get; set; }
    // ...
}

[Table("Tenant")]
public class Tenant : UserProfile
{
    public string PersonalDescription { get; set; }
    // ...

    // Navigation property on dependant end
    public virtual UserProfile UserProfile { get; set; }
}

• Am I correct in placing the navigation property on the dependant end of the relationship? Or does it matter what end it goes on?

• Would I need to also place a navigation property of type Tenant in UserProfile ?

• Finally, I read that it is worthwhile making every property in a model virtual to help EF with change tracking - is this necessary?

Answer 1

In a table-per-type scenario you do not need navigation properties. Tenant does not contain a UserProfile, Tenant is a UserProfile.

EF should be able to get the values of the Tenant fields from the Tenant table, and the fields inherited from UserProfile from the UserProfile table. Looks magical, but it works, at least for me :)

As for the DbSets, if you need to directly use a Tenant collection, you could add a Tenants DbSet. That would enable you to do:

myContext.Tenants.Where(t => ... t.PersonalDescription ... t.UserId ...)

which is equivalent with the longer and less discoverable

myContext.UserProfiles.OfType<Tenant>.Where(t => ....)

My personal preference is not to use the declared DbSets at all, and use the Set<T>() method directly in a wrapping repository, that exposes methods like GetByKey , Update etc.., but that is a matter of taste.