How to design DTO about Intersection Entity with attribute

I'm wondering How I can design DTO about Intersection Entity (about many-to-many relation) with attribute.

For example, if there was CAR, PARTS, CAR_PARTS table, like

CAR (ID, NAME, ...)
PARTS (ID, NAME, ...)
CAR_PARTS (CARID, PARTSID)

, and let CAR and PARTS have many-to-many relation, then I think we can design DTO as

class Car {
    int id;
    String Name;
    List<Parts> partsList;
}
public class Parts {
    int id;
    Str开发者_JS百科ing name;
    List<Car> carList;  //if necessary
}

It's OK.

The question is, if CAR_PARTS table had any attribute, like

CAR (ID, NAME, ...)
PARTS (ID, NAME, ...)
CAR_PARTS (CARID, PARTSID, QUANTITY)

, and here QUANTITY indicates the parts quantity in a car, for example if a car has 4 tyres then QUANTITY is 4, in this case how I can design DTO?

In the classes above they expresses the relationship as having the property of each class. So it seems not to be able to express quantity...

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Why not make dictionary like Dictionary<Parts, Qty> partsList; or Make List<CAR_PARTS> parts; and have car_parts class with required attribute