c# Linq sort List by member of nested List

Question

I've got

List<ObjectA> 
ObjectA is a List<ObjectB> 
ObjectB is List<ObjectC>

One of ObjectC is class with field ID (I could specify it) and field "Name"

var result = List<ObjectA>
.OrderBy(t => t.ObjectB[1]    
.ObjectC   
.Where(c => c.ID.Equals("ID"))  
.FirstOrDefault().Name)

• it works.

I want to NOT use strong index for ObjectB. Something like

var result = List<ObjectA>
.OrderBy(t => t.ObjectB.Where(s=>s
.ObjectC
.Where(c => c.ID.Equals("ID"))
.FirstOrDefault().Name)

• of course it not works:).

So, how could I sort List by Name?

Thanks.

Answer 1

It seems that you can leverage using SelectMany to flatten the nested collections. Should look something like this:

var result = List<ObjectA>
    .OrderBy(t => t.ObjectB
        .SelectMany(s => s.ObjectC)
        .Where(c => c.ID.Equals("ID"))
        .FirstOrDefault()?.Name)