using System;

using System.Diagnostics;

public class Program

{

    private static TimeSpan DoStuff(TimeSpan t) { return t; }

    public static void Main()

    {

        object o1 = TimeSpan.FromSeconds(123);

        int x = 3;

​

        var sw = new Stopwatch();

        int i;

        // Here please note that first loop does type check (always true) and always-false int check - no actual cast

        // while second does type check (always true) with cast in-place. None of those loops actually call DoStuff

        // You may switch loops order for testing, it doesn't matter

        sw.Restart();

        for (i = 0; i < 1000000; ++i) {

            if (o1 is TimeSpan && x == 7) {

                DoStuff((TimeSpan)o1);

            }

        }

        sw.Stop();

        Console.WriteLine(sw.ElapsedTicks);

        sw.Restart();

        for (i = 0; i < 1000000; ++i) {

            if (o1 is TimeSpan t1 && x == 7) {

                DoStuff(t1);

            }

        }

        sw.Stop();

        Console.WriteLine(sw.ElapsedTicks);

​

        // Below both loops do type check and casting and call DoStuff (that's why tick-results are generally higher)

​

        sw.Restart();

        for (i = 0; i < 1000000; ++i) {

            if (o1 is TimeSpan) {

                DoStuff((TimeSpan)o1);

            }

        }

        sw.Stop();

        Console.WriteLine(sw.ElapsedTicks);

        sw.Restart();

        for (i = 0; i < 1000000; ++i) {

            if (o1 is TimeSpan t1) {

                DoStuff(t1);

            }

        }

        sw.Stop();

        Console.WriteLine(sw.ElapsedTicks);

​

    }

}