在EntityFramework 6中将父实体更改为子实体

Question

I have the following hierarchy models in Entity Framework 6.

ChildUser Inherits ParentUser. ParentUser has less fields than ChildUser and I am using the Table Per Hierarchy (TPH) inheritance structure of EF6.

In some situations the ParentUser is upgraded to ChildUser, so what is the best way to manage this?

// Naive way that doesn't work and doesn't take into account changing the discriminator
ParentUser parentUser = ctx.ParentUsers.Single(x => x.Id == 1);
ChildUser childUser = (ChildUser)parentUser;
childUser.ExtraField = "Some Value";
ctx.SaveChanges();

Any pointers to the right directions are appreciated.

Answer 1

Create a new ChildUser object, add the father params and add this new child to the DB

ChildUser childUser = new ChildUser();
ParentUser parentUser = ctx.ParentUsers.Single(x => x.Id == 1);

childUser.param1 = parentUser.param1;
....
childUser.ExtraField = "Some Value";
ctx.ChildUsers.Add(childUser); //Add the new child
ctx.ParentUsers.Remove(parentUser); //If you wanna remove the parent too
ctx.SaveChanges();