Dealing with infinity

gistfile1.cs

        // you can do this even with BigInteger
        static IEnumerable<long> AllNumbers()
        {
            var x = 0;
            while (true)
                yield return x++;
        }

        static IEnumerable<long> AllEvenNumbers()
        {
            return AllNumbers().Where(x => x % 2 == 0);
        }

        static void Main(string[] args)
        {
            foreach (var evenNumber in AllEvenNumbers().TakeWhile(x => x < 100))
            {
                Console.WriteLine(evenNumber);
            }

            Console.ReadKey();
        }