添加项目到集合集合

Question

这是我的对象结构中，

Group has   
    List of Offers 
Offer has 
    GroupId 
    List of Products 

我如何将产品添加到基于组ID的产品已经存在的列表

该代码添加产品覆盖，但现有产品

Group.OffersList.Where(x => x.GroupId == "1") 
       .SelectMany(x => x.ProductList) 
       .ToList().Add(Product); 

Answer 1

Group.OffersList.Where(x => x.GroupId == "1") 
       .ToList() 
       .ForEach(x => x.Add(Product));