C# – Deleting Entity in Entity Model gives Foreign Key errors

I've found the Entity Framework designer leaves a lot to be desired so I found the best way is to edit the .edmx by hand.

The .edmx file contains 3 main sections, one which represents the storage model (database), one which represents the conceptual model and one section which represents the mapping between the two models

If I understand correctly, you have removed Table2 from the conceptual model and so you should remove anything related to it in the conceptual side of the EDMX. Chances are table 1 will still have an association to table 2 that you need to delete. Unfortunately manual edits to the .EDMX file will be overwritten if you ever use the designer to regenerate the model.

Because Stage is required, all one-to-many relationships where Stage is involved will have cascading delete enabled by default. It means, if you delete a Stage entity

• the delete will cascade directly to Side
• the delete will cascade directly to Card and because Card and Side have a required one-to-many relationship with cascading delete enabled by default again it will then cascade from Card to Side

So, you have two cascading delete paths from Stage to Side - which causes the exception.

You must either make the Stage optional in at least one of the entities (i.e. remove the [Required] attribute from the Stage properties) or disable cascading delete with Fluent API (not possible with data annotations):

modelBuilder.Entity<Card>()
    .HasRequired(c => c.Stage)
    .WithMany()
    .WillCascadeOnDelete(false);

modelBuilder.Entity<Side>()
    .HasRequired(s => s.Stage)
    .WithMany()
    .WillCascadeOnDelete(false);