How can I measure which one is faster? - C#

Question

Hello,

I wrote a program with two approaches. How can I measure which one is faster?

Thank you

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;

namespace HelloWorld
{

    class Program
    {
        static void Main(string[] args)
        {
            string path = @"G:\";
            ShowBasedSized(path);
            Console.WriteLine();
            ShowBasedSizedWithLinq(path);
        }

        private static void ShowBasedSizedWithLinq(string path)
        {
            var result = from file in new DirectoryInfo(path).GetFiles()
                         orderby file.Length
                         select file;

            foreach (var item in result)
            {
                Console.WriteLine($"{item.Name,-30} - {item.Length,10}");
            }

        }

        private static void ShowBasedSized(string path)
        {
            DirectoryInfo directoryInfo = new DirectoryInfo(path);
            FileInfo[] fileInfos = directoryInfo.GetFiles();

            Array.Sort(fileInfos, new SortFilesBasedSized());

            foreach (FileInfo item in fileInfos)
            {
                Console.WriteLine($"{item.Name,-30} - {item.Length,10}");
            }
        }


    }
    public class SortFilesBasedSized : IComparer<FileInfo>
    {
        public int Compare(FileInfo first, FileInfo second)
        {
            return first.Length.CompareTo(second.Length);
        }
    }
}

Answer 1

The main difference, is linq orderby and array sort uses different algorithms. Linq uses a stable quick sort so it can be applied multiple times, and array sort uses different algorithms based on size. Both of these sorts speed is effected by the data (how random the key is and the number of keys).

As suggested, the directory lookup is the most expensive operations, making the sort time mote.

Answer 2

Use a StopWatch

Stopwatch stopwatch = Stopwatch.StartNew();
// call your method
stopwatch.Stop();

Debug.WriteLine($"Time taken: {stopwatch.Elapsed.TotalMilliseconds} ms" );

stopwatch.Reset();
stopwatch.Start();
// next method
Debug.WriteLine($"Time taken: {stopwatch.Elapsed.TotalMilliseconds} ms");