ADO.NET EF Composite primary key - can not update foreign key

Question

I have following entities:

In my code i need to update the FKCategoryID in entity BudgetPost but im getting error:

FKCategoryID is part of the object's key information

Is it any way to update the key in this case or it's not possible?

Thanks in advance

Answer 1

Why is it a part of the composite key? As long as FKBudgetID is a part of the composite primary key you won't be able to modify it. If you want to enforce uniqueness in the combination of FKCategoryID and FKBudgetID, use a UNIQUE constraint instead.