Question

Below have a simple piece of code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace LinqStuff
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            var aS = new List<A>();
            aS.Add(new A { aId = 0 });
            aS.Add(new A { aId = 1 });

        var bs = new List<B>();
        bs.Add(new B { aId = 0, bId = 0 });
        bs.Add(new B { aId = 0, bId = 1 });

        var cs = new List<C>();
        cs.Add(new C { bId = 0, cId = 0, Val = 100 });
        cs.Add(new C { bId = 0, cId = 1, Val = 100 });
        cs.Add(new C { bId = 1, cId = 2, Val = 100 });
        cs.Add(new C { bId = 1, cId = 3, Val = 100 });


    }
}

internal class A
{
    public int aId { get; set; }
}

internal class B
{
    public int aId { get; set; }
    public int bId { get; set; }
}

internal class C
{
    public int bId { get; set; }
    public int cId { get; set; }
    public int Val { get; set; }
}

}

What i would like to do is to have alinq that will bring me back 2 anonymous objects like this:

First: (aid = 1, Sum = 0)
Second: (aid = 0, Sum = 400)

The Sum is the sum of all objects C that are linked through B with A.

I tried with SelectMany but I never get further than getting back 5 pairs of (A, C) that i need to perform grouping on later.

E.g.

            var result = aS.SelectMany(a => bs.Where(b => b.aId == a.aId).DefaultIfEmpty(),
                                        (a, b) => new { A = a, B = b })
                            .SelectMany(b => cs.Where(c => b != null && b.B != null && c.bId == b.B.bId).DefaultIfEmpty(),
                                        (b, c) => new { A = b.A, C = c })

Something is missing, could you please help me?

Cheers.

Answer 1

Not the most beautiful Linq statement, but this should do it;

var result = aS.Select(a => 
  new { a.aId, 
        sum = cs.Where(c => bs.Where(b => b.aId == a.aId)
                .Select(b => b.bId)
                .Contains(c.bId))
                .Sum(c => c.Val) 
      }).ToList();