Create IGrouping within IGrouping

Question

I have a List of flat ViewModels.

var initialList = new List<ViewModel>
{
    new ViewModel { OuterCaption = "A outer", InnerCaption = "A inner", Caption = "E", Id = 8},
    new ViewModel { OuterCaption = "B outer", InnerCaption = "B inner", Caption = "A", Id = 5},
    new ViewModel { OuterCaption = "A outer", InnerCaption = "B inner", Caption = "A", Id = 12},
    new ViewModel { OuterCaption = "B outer", InnerCaption = "B inner", Caption = "B", Id = 9},
    new ViewModel { OuterCaption = "A outer", InnerCaption = "B inner", Caption = "B", Id = 23},
    new ViewModel { OuterCaption = "B outer", InnerCaption = "C inner", Caption = "A", Id = 10},
    new ViewModel { OuterCaption = "A outer", InnerCaption = "B inner", Caption = "C", Id = 16},
    new ViewModel { OuterCaption = "A outer", InnerCaption = "A inner", Caption = "C", Id = 4},
    new ViewModel { OuterCaption = "A outer", InnerCaption = "A inner", Caption = "D", Id = 7},
    new ViewModel { OuterCaption = "C outer", InnerCaption = "A inner", Caption = "A", Id = 31},
    new ViewModel { OuterCaption = "B outer", InnerCaption = "A inner", Caption = "A", Id = 19},
    new ViewModel { OuterCaption = "B outer", InnerCaption = "A inner", Caption = "B", Id = 20},
    new ViewModel { OuterCaption = "A outer", InnerCaption = "A inner", Caption = "A", Id = 1},
    new ViewModel { OuterCaption = "A outer", InnerCaption = "A inner", Caption = "B", Id = 3}
}.OrderBy(vm => vm.OuterCaption).ThenBy(vm => vm.InnerCaption).ThenBy(vm => vm.Caption);

Where each ViewModel is as the following.

class ViewModel
{
    public string OuterCaption { get; set; }
    public string InnerCaption { get; set; }
    public string Caption { get; set; }
    public int Id { get; set; }

}

Now I want to group the List by the OuterCaption and later by the InnerCaption. I can group the List by the OuterCaption like this.

var list = initialList.GroupBy(vm => vm.OuterCaption).ToList();

And use it in my View like this and use GroupBy within my View.

foreach (var outerGrouping in list)
{
    Console.WriteLine(outerGrouping.Key);
    Console.WriteLine("~~~~~~~~~~~~~~~~~~");

    foreach (var innerGrouping in outerGrouping.GroupBy(vm => vm.InnerCaption))
    {
        Console.WriteLine(innerGrouping.Key);

        foreach (var vm in innerGrouping)
        {
            Console.WriteLine("Caption: " + vm.Caption + " Id:" + vm.Id);
        }

        Console.WriteLine("------------------");
    }

    Console.WriteLine("~~~~~~~~~~~~~~~~~~");
}

But I'd like to create a IGrouping within a IGrouping and not use GroupBy (or Linq) in my View. I do think that I should create something like IReadOnlyList<IGrouping<string, IGrouping<string, ViewModel>>> (might be wrong) for my View. How do I achieve this with my initialList so I can remove Linq from my View?

Here is the example code: https://dotnetfiddle.net/hP2kxO

Answer 1

This is working. It's not exactly what I'm looking for but it removes Linq from my View.

var list = initialList
    .GroupBy(vm => (vm.OuterCaption, ViewModel: vm))
    .GroupBy(group => group.Key.ViewModel.InnerCaption)
    .ToList();