Question

Apologies for the clunky title. I need to query a collection and return the grandparent, parent and grandchild based on a grandchild’s property

For example with the object below, I want to get the Quote, the Rate (Parent) and the Plan (GrandChild) only if a condition matches the Plan’s ID.

public class Quote
{
    public int Id { get; set; }
    public string Type { get; set; }
    public string ParentType { get; set; }
    public decimal ValueMax { get; set; }
    public virtual ICollection<Rate> Rates { get; set; }
}

public class Rate
{
    public int Id { get; set; }
    public decimal ValueMax { get; set; }
    public ICollection<Plan> Plans { get; set; }
}

public class Plan

    public int Id { get; set; }
    public decimal Price { get; set; }
}

Answer 1

You should be able to do something like this to get the plans which meet whatever criteria, along with their parent and grandparent objects:

// results is an anonymous type with properties Quote, Rate, Plan
var results = from q in quotes
    from r in q.Rates
    from p in r.Plans
    where p.Id < 500 /* whatever criteria */
    select new 
    {
        Quote = q,
        Rate = r,
        Plan = p
    };