using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        List<int> numbers = new List<int>{0};

        Func<int, bool> comparator = t => t < 3;

        var lookup = numbers.ToLookup(i => comparator(i));

        var listWhereTrue = lookup[true].ToList();

        var listWhereFalse = lookup[false].ToList();

        Console.WriteLine(listWhereTrue.Count);

        Console.WriteLine(listWhereFalse.Count);

    }

}