using System;

using System.Diagnostics;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    struct Test

    {

        public string Value;

        public int Number;

        public Test(string s)

        {

            Value = s;

            Number = s.GetHashCode();

        }

    }

    private static List<string> WithoutLinq(List<Test> input)

    {

        List<string> output = new List<string>();

        foreach (var x in input)

        {

            output.Add(x.Value);

        }

        return output;

    }

    private static List<string> WithLinq(List<Test> input)

    {

        return (from x in input select x.Value).ToList();

    }

    private static void Optimal(List<Test> input, List<string> output)

    {

        output.Clear();

        foreach (var x in input)

        {

            output.Add(x.Value);

        }

    }

    private static void Benchmark(Action act, int iterations)

    {

        GC.Collect();

        act.Invoke(); // run once outside of loop to avoid initialization costs

        Stopwatch sw = Stopwatch.StartNew();

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

        {

            act.Invoke();

        }

        sw.Stop();

        Console.WriteLine((sw.ElapsedTicks).ToString());

    }

​

    private static Random random = new Random();

​

    // Ironic

    public static string RandomString(int length)

    {

        const string chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";

        return new string(Enumerable.Repeat(chars, length)

            .Select(s => s[random.Next(s.Length)]).ToArray());

    }

    public static void Main(string[] args)

    {

        List<string> forOptimal = new List<string>();

        List<Test> inputs = new List<Test>();

        const int testInputNum = 100;

        for (int i = 0; i < testInputNum; i += 1)

        {

            inputs.Add(new Test(RandomString(5)));

        }

        Benchmark(() => { List<string> o = WithLinq(inputs); }, 1000);

        Benchmark(() => { List<string> o = WithoutLinq(inputs); }, 1000);

        Benchmark(() => { Optimal(inputs, forOptimal); }, 1000);

    }

}