CastClassVsIsInst.cs

namespace CastClassVsIsInst
{
    using System;
    using System.Diagnostics;

    class Program
    {
        private class Blah { }
        static void Main(string[] args)
        {
            object instance = new Blah();
            Measure(() => { var copy = (Blah)instance; }, 5);
            Measure(() => { var copy = instance as Blah; }, 5);
            Console.ReadKey();
        }

        private static void Measure(Action action, int times)
        {
            action();
            for (var time = 0; time < times; time++)
            {
                var watch = Stopwatch.StartNew();
                for (var iteration = 0; iteration < int.MaxValue; iteration++)
                {
                    action();
                }
                watch.Stop();
                Console.WriteLine(watch.Elapsed);
            }
            GC.Collect();
        }
    }
}