private void Fixupcustomer_type(customer_type previousValue) { if (previousValue != null && previousValue.customers.Contains(this)) { previousValue.customers.Remove(this); } if (customer_type != null) { if (!customer_type.customers.Contains(this)) { customer_type.customers.Add(this); } if (type_id != customer_type.id) { type_id = customer_type.id; } } else if (!_settingFK) { type_id = null; } }