using System;

using System.Collections.Generic;

using System.Linq;

using System.Diagnostics;

​

public class Program

{

    public static void Main()

    {

        IEnumerable<Item> items = new List<Item>(Enumerable.Range(0,1000).Select(a=> new Item(a)));

        // sorting randomly

        items = items.OrderBy( x=> new Guid()).ToList().ToArray();

        Func<Item,bool> filter = x => x.Size == 500;

        Run("First", () => items.First( filter ));

        Run("Where First", () => items.Where( filter ).First());

        filter = x => x.Size < 500;

        Run("First", () => items.First( filter ));

        Run("Where First", () => items.Where( filter ).First());

        filter = x => x.Size > 500;

        Run("First", () => items.First( filter ));

        Run("Where First", () => items.Where( filter ).First());

    }

    public class Item{

        public String Name{ get;set; }

        public int Size {get;set;}

        public Item(int n){

            Size = n;

            Name = "a" + Size;

        }

    }

    public static void Run(String title, Func<object> action){

        Stopwatch watch = Stopwatch.StartNew();

        for(int i=0;i<10000;i++){

            action();

        }

        watch.Stop();

        Console.WriteLine("{0} milliseconds for {1}", watch.ElapsedMilliseconds, title);

    }

}

​

​

​