linq aggregated nested count

Question

i have the following classes:

class Outer
{
   public ICollection<Inner> Inners
}

class Inner
{
    public ICollection<Inner> Inners
}

I would like to order descending a list of outers by the total count of their Inners and nested Inners.

for example:

if i have 2 outers: the first has a collection of 3 inners, each with 1 nested inner then total is 5.

the second has for example can have a collection of 2 inners, each with 3 nested inner then the total count is 2 + 3 + 3 = 8

therefor in the returned result the second example should be the first.

Anyone? :)

Shouldn't the total in the first example be 6, or am I misunderstanding something? — Joachim Isaksson, Aug 04 '13 at 08:16

score 3 · Accepted Answer · answered Aug 04 '13 at 08:42

First, build a recursive method to count the Inner objects inside a Inner object including itself:

public static int Count(Inner inner)
{
    var count = 1;
    if (inner.Inners != null && inner.Inners.Any())
       count += inner.Inners.Sum(x => Count(x));

    return count;
}

Then you can order:

var result = outers.OrderBy(o => o.Inners.Sum(i => Count(i)));

linq aggregated nested count

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