using System;

using System.Linq;

public class SumCount

{

    public static void Main()

    {

        var arr = new int[] { 1,2,3,4,5,6 };

        Console.WriteLine(arr.Where(n=>n%2==0).Sum()); // 12

        Console.WriteLine(arr.Sum(n=>n%2==0 ? n : 0)); // 12

        Console.WriteLine(arr.Count(n=>n<4)); // 3

    }

}