I have an administrative staff, account manager and customer. The administrative staff creates a new customer. After this, the administrative staff selects an account manager for the customer. Based on an attribute of the current user (administrative staff) also a list of products should be added to this customer. For example administrative staff with attribute toys-steel has another list of products as administrative staff with toys-wood. The administrative staff creates this list in a datagrid. The domain model consists of administrative staff, account manager, customer and product list. For an unique customer I want to create an unique list of products from an existing list. The reason why I want to do this is because if I link a customer to a product list, changes made by this customer applies to all the others with the same relation. Is there a way to create an unique list?
Also not completely sure if I get the question. But in general, if you perform a Union of two lists, the result will not contain duplicates.
If you want to remove duplicates from a single list, do a Union on it with itself.
I'm not sure if I understand you correctly, but from your description I would to the following:
Add an extra entity e.g. 'CustomerProduct' with a associations to both Customer and product.
The entity should also contain the attributes a customer is allowed to edit.