Maintaining a two way relationship between classes

Question

It is pretty common, especially in applications with an ORM, to have a two way mapping between classes. Like this:

public class Product
{
    private List

        

Answer 1

I am just now working on a problem similar to this and I am using #3 in LBushkin's answer.

I have a data storage object with lists for all of my data classes. The data classes have ids in them for references to the other classes and I call back to the data storage class to get the reference item.

I have found this really useful because I need to be able to filter the data and that is done when requesting the data from the data storage.