c＃在类中列出

This a fairly simple question, I have 3 classes (see code below) called projects, sites and wells. The projects class will be a list, but I would like it to contain a list of the sites and then the sites list will contain a list of wells. Not sure if that's allowed. I did a bit of searching and most of the solutions I saw talked more about how to create a list type without knowing what class it was going to be. I know what mine are going to be, so that's not an issue here.This a fairly simple question, I have 3 classes