Why is there no update equivalent to WillCascadeOnDelete?

Question

When you're setting up a one:many relationship in EF code-first, you can choose whether it should cascade on delete like so:

modelBuilder.Entity<Assessment>()
    .HasRequired(asmt => asmt.CreatedByUser)
    .WithMany(usr => usr.Assessments)
    .HasForeignKey(asmt => asmt.CreatedByUserId)
    .WillCascadeOnDelete(true);

This translates to the SQL ON DELETE CASCADE part of a foreign key definition, ie.

ALTER TABLE [dbo].[Assessment]  WITH CHECK ADD  CONSTRAINT [FK_dbo.Assessment_dbo.User_CreatedById] FOREIGN KEY([CreatedById])
REFERENCES [dbo].[User] ([UserId])
ON DELETE CASCADE
GO

However, there doesn't seem to be a similar method in the Fluent API that allows you to control the value of ON UPDATE CASCADE, ie. something like .WillCascadeOnUpdate(). Why not?

Answer 1

Well, apparently the answer to this is that you should never change the primary key in an ORM, even though DBMS's support the changing of the primary key. Because the assumption is that you will never change the primary key, there's no need for entity framework to allow you to specify whether to cascade on update, because the idea is that that primary key update will never happen.

Note, though, that this can still be done manually in most databases even if the entity framework ORM doesn't let you do it that way. The DBMS will just use its default behaviour for a cascade update if you do the primary key update, manually, directly in the database.