using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        int[] arr = { 3, -4, 2, 9, 0, 7, -2, 1, 6, 5, 4 };

        int target = 5;

        var result = FindIndicesOfSum(arr, target);

        if (result != null)

        {

            Console.WriteLine(new { Index1 = result[0], Index2 = result[1] });

        }

    }

    private static int[] FindIndicesOfSum(int[] array, int target)

    {

        var query =

            from x in array.Select((value, idx) => new { value, idx })

            from y in array.Select((value, idx) => new { value, idx })

            where (x.idx != y.idx) && ((x.value + y.value) == target)

            select new[] { x.idx, y.idx };

        var result = query.FirstOrDefault();

        return result;

    }

}