How to disable cascade delete for link tables in EF code-first?

Question

I want to disable cascade deletes for a link table with entity framework code-first. For example, if many users have many roles, and I try to delete a role, I want that del

Answer 1

I believe that turning off ManyToManyCascadeDeleteConvention globally is not a wise option. Instead, it's better to turn it off only for the concerned table.

This can be achieved through editing the generated migration file, for property cascadeDelete. For example:

AddForeignKey("dbo.UsersRoles", "UserId", "dbo.User", "UserId", cascadeDelete: false);

Answer 2

I agree with Ebram Khalil that turning it off for a single table is a good option. I like to stick as close to the automatically built migrations as I can, however, so I would set it up in OnModelCreating:

modelBuilder.Entity<User>()
    .HasMany(usr => usr.Roles)
    .WithMany(role => role.Users)
    .Map(m => {
        m.ToTable("UsersRoles");
        m.MapLeftKey("UserId");
        m.MapRightKey("RoleId");
    })
    .WillCascadeOnDelete(false);

I believe this preserves the delete going the other direction, so if both needed to be blocked (makes sense in this example) a similar call would need to be made starting with Entity<User>(Role)

Of course, this comes ages after the question was asked. So it may not have been valid in 2012.

Answer 3

I got the answer. :-) Those cascade deletes were being created because of ManyToManyCascadeDeleteConvention. You need to remove this convention to prevent it from creating cascade deletes for link tables:

modelBuilder.Conventions.Remove<ManyToManyCascadeDeleteConvention>();