【C#/LINQ】Dictionaryの値の取得方法について時間を比較する

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;

namespace DictionaryGetter
{
    class Program
    {
        private static int DATA_COUNT = 10000;

        static void Main(string[] args)
        {
            // アクセス用ディクショナリを作る
            var dict = Enumerable
                .Range(0, DATA_COUNT)
                .Select(x => new { Id = Guid.NewGuid(), Data = "data" })
                .ToDictionary(x => x.Id);

            // キーの値をシャッフルし、配列にしておく
            var keys = dict.Keys
                .OrderBy(key => Guid.NewGuid())
                .ToArray();


            var watch = new Stopwatch();

            // インデクサ
            watch.Reset();
            watch.Start();
            foreach (var key in keys)
            {
                var val = dict[key];
            }
            watch.Stop();
            Console.WriteLine("use indexer:\t" + watch.Elapsed.ToString());


            // First()メソッド
            watch.Reset();
            watch.Start();
            foreach (var key in keys)
            {
                var val = dict.First(x => x.Key == key);
            }
            watch.Stop();
            Console.WriteLine("use First():\t" + watch.Elapsed.ToString());


            // Single()メソッド
            watch.Reset();
            watch.Start();
            foreach (var key in keys)
            {
                var val = dict.Single(x => x.Key == key);
            }
            watch.Stop();
            Console.WriteLine("use Single():\t" + watch.Elapsed.ToString());
        }
    }
}

use indexer: 00:00:00.0010259
use First(): 00:00:02.9547870
use Single(): 00:00:05.8560762
続行するには何かキーを押してください . . .