MontyHall.cs

using System;
using C = System.Console;

namespace MontyHall
{
    class Program
    {

        static void Main(string[] args)
        {
            int[] Doors = new int[3];
            const int times = 1000000;
            Random rnd = new Random();
            int totalWins = 0;

            //Loop times times, not switching
            for (int i = 0; i < times; i++)
            {
                //Construct new doors, populate one with 1
                Doors = new int[3] { 0, 0, 0 };
                Doors[rnd.Next(1, 4) - 1] = 1;

                //Guess any random door
                totalWins += Doors[rnd.Next(1, 4) - 1];
            }

            C.WriteLine("No Switch:  {0} / {1}", totalWins, times);
            C.WriteLine("Yes Switch: {0} / {1}", (times - totalWins), times);
            C.ReadKey();
        }
    }
}