using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        List<int> fullList = new List<int> { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };

        IEnumerable<int> evenNumbers = fullList.Where(n => IsEven(n));

        //IEnumerable<int> evenNumbers = fullList.Where(n => IsEven(n)).OrderBy(n => n);

        //IEnumerable<int> evenNumbers = GetEvenNumbers();

        Console.WriteLine("-- Checking if even numbers exist (Any) --");

        Console.WriteLine("Even numbers exist? " + evenNumbers.Any());

        Console.WriteLine();

        Console.WriteLine("-- Checking how many even numbers exist (Count) --");

        Console.WriteLine("Number of even numbers: " + evenNumbers.Count());

        Console.WriteLine();

        Console.WriteLine("-- Getting the first even number (First) --");

        Console.WriteLine("First even number: " + evenNumbers.First());

        Console.WriteLine();

        Console.WriteLine("-- Getting the last even number (Last) --");

        Console.WriteLine("Last even number: " + evenNumbers.Last());

        Console.WriteLine();

        Console.WriteLine("-- Iterating over the even numbers (foreach --");

        foreach (var evenNumber in evenNumbers)

        {

            Console.WriteLine("Even number: " + evenNumber);

        }

        Console.WriteLine();

    }

    public static bool IsEven(int number)

    {

        Console.WriteLine("Checking number " + number + " for evenness.");

        return number % 2 == 0;

    }

    public static IEnumerable<int> GetEvenNumbers()

    {

        for (var i = 0; i < 10; i += 2)

        {

            Console.WriteLine("Found even number " + i + ".");

            yield return i;

        }

    }

}