using System;

using System.Diagnostics;

using System.Collections;

using System.Linq;

public class Program

{

    private const int Iterations = 190000;

    public static void Main()

    {

        var sw = new Stopwatch();

        sw.Start();

        for (int i = 0; i < Iterations; i++)

        {

            IEnumerator enumerator = YieldBreak();

            while(enumerator.MoveNext())

            {

                throw new InvalidOperationException("Should not occur");

            }           

        }

        sw.Stop();

        Console.WriteLine("Yield break: {0}", sw.Elapsed);

        GC.Collect();

        sw.Restart();

        for (int i = 0; i < Iterations; i++)

        {

            IEnumerator enumerator = Enumerable.Empty<object>().GetEnumerator();

            while(enumerator.MoveNext())

            {

                throw new InvalidOperationException("Should not occur");

            }           

        }

        sw.Stop();

        Console.WriteLine("Enumerable.Empty<T>(): {0}", sw.Elapsed);

        GC.Collect();

        sw.Restart();

        var instance = new EmptyEnumerator();

        for (int i = 0; i < Iterations; i++)

        {

            while(instance.MoveNext())

            {

                throw new InvalidOperationException("Should not occur");

            }           

        }

        sw.Stop();

        Console.WriteLine("EmptyEnumerator instance: {0}", sw.Elapsed);

    }

    public static IEnumerator YieldBreak()

    {

        yield break;

    }

    private class EmptyEnumerator : IEnumerator

    {

        //public static readonly EmptyEnumerator Instance = new EmptyEnumerator();

        public bool MoveNext()

        {

            return false;

        }

        public void Reset()

        {

        }

        public object Current { get { return null; } }

    }

}