using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        var dnaGenerator = new DnaGenerator();

        Console.WriteLine($"TotalMemory: {GC.GetTotalMemory(true):#,0} bytes");

        DoWork(dnaGenerator);

        GC.Collect();

        Console.WriteLine($"TotalMemory: {GC.GetTotalMemory(true):#,0} bytes");

        GC.KeepAlive(dnaGenerator);

​

        static void DoWork(DnaGenerator dnaGenerator)

        {

            foreach (string dna in dnaGenerator.Take(5))

            {

                Console.WriteLine($"Processing DNA of {dna.Length:#,0} nucleotides, starting from {dna[0]}");

            }

        }

    }

​

    class DnaGenerator : IEnumerable<string>

    {

        private readonly IEnumerable<string> _enumerable;

​

        public DnaGenerator() => _enumerable = Iterator();

​

        private IEnumerable<string> Iterator()

        {

            while (true)

                foreach (char c in new char[] { 'A', 'C', 'G', 'T' })

                    yield return new String(c, 10_000_000);

        }

​

        public IEnumerator<string> GetEnumerator() => _enumerable.GetEnumerator();

        IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();

    }

}

​