Query that Groups Parent, then Child, when fetching from IQueryable<GrandChild> - linq

Question

Lets imagine that below is our data model. I want to query the Toys but have the results returned such that I can do the following psuedo code.
foreach (var parent in parents)
{
Console.WriteLine(parent.Name);
foreach (var child in parent.Children)
{
Console.WriteLine(child.Name);
foreach (var toy in child.Toys)
{
Console.WriteLine(toy.Name);
}
}
}
The data model:
public class Parent
{
public Guid ParentId { get; set; }
public String Name { get; set; }
public ICollection<Child> Children { get; set; }
}
public class Child
{
public Guid ChildId { get; set; }
public Guid ParentId { get; set; }
public Parent Parent { get; set; }
public String Name { get; set; }
public ICollection<Toy> Toys { get; set; }
}
public class Toy
{
public Guid ToyId { get; set; }
public Guid ChildId { get; set; }
public Child Child { get; set; }
public String Name { get; set; }
public bool IsCool { get; set; }
}
I've tried doing this with grouping but when I try to iterate a grouping all that I see is Key which doesn't have any properties on it so I can't get the Parent.Name or the Child.Name.
Thanks in advance.

Answer 1

You can do:
var query = from p in parents
from c in p.Children
from t in c.Toys
select new { Parent = p.Name, Child = c.Name, Toy = t.Name }
foreach (var a in query)
{
// write values.
}
In effect, this uses SelectMany.
Edit
After your comment, I think what you're looking for is not a grouping. If you've got a Parent object in fact its Children are already grouped inside of it, because each parent has its own collection. But maybe you're looking for a way to populate the collections? That would be done by
var query = from p in parents.Include(x => x.Children.Select(c => c.Toys));

Answer 2

With LazyLoadingEnabled set to be false, you will be able to do this by using one linq query to load all related objects.
Please note, this may cause some performance issue if you have great amount of related data in Children or Toys table.
context.ContextOptions.LazyLoadingEnabled = false;
var parents = context.Parents.Select(x=>x).ToList();
foreach(var parent in parents) {
Console.WriteLine(parent.Name);
foreach(var child in parent.Children) {
Console.WriteLine(child.Name);
foreach(var toy in child.Toys) {
Console.WriteLine(toy.Name);
}
}
}