using System;

using System.Collections.Generic;

using System.Diagnostics;

​

class A {}

class B {}

class C {}

​

public class Program

{

    const int iterations = 1000;

    private static void Benchmark(string name, Action act)

    {

        GC.Collect();

        act.Invoke(); // run once outside of loop to avoid initialization costs

        Stopwatch sw = Stopwatch.StartNew();

        for (int i = 0; i < iterations; i++)

        {

            act.Invoke();

        }

        sw.Stop();

        Console.WriteLine(name + ": " + (sw.ElapsedTicks).ToString());

    }

​

    private static int CountInObjects(object[] objects) {

        int count = 0;

        foreach (object o in objects) {

            A a = o as A; // cast

            if (a != null) {

                count += 1;

            }

        }

        return count;

    }

    private static int CountInDict(Dictionary<int, object> dict) {

        int count = 0;

        foreach (KeyValuePair<int, object> pair in dict) {

            if (pair.Key != 0) {

                count += 1;

            }

        }

        return count;

    }

    public static void Main(string[] args)

    {

        Random rng = new Random();

        object[] objects = new object[10000];

        for (int i = 0; i < objects.Length; i++) {

            switch (rng.Next(3)) {

                case 0: objects[i] = new A(); break;

                case 1: objects[i] = new B(); break;

                case 2: objects[i] = new C(); break;    

            }

        }

        Dictionary<int, object> dict = new Dictionary<int, object>();

        for (int i = 0; i < objects.Length; i++) {

            dict[i] = new object();

        }

        int useInt = 0;

        Benchmark("cast", () => useInt += CountInObjects(objects));

        Benchmark("lookup", () => useInt += CountInDict(dict));

        Console.WriteLine("\n\nignore me: " + useInt.ToString());

    }

}