Performance Test Sparse/Dense Random Object Storage

using System;
using System.Collections.Generic;
using System.Diagnostics;

namespace ConsoleTests
{

    class Program
    {

        static void Main(string[] args)
        {
            Random rnd = new Random((int)DateTime.Now.Ticks);

            MyList<int> listType = new MyList<int>();
            MyCoolType<int> coolType = new MyCoolType<int>();

            Stopwatch sw = new Stopwatch();
            sw.Start();

            Console.WriteLine("Inserting into MyList<int>");

            for (int i = 0; i < 1000000; i++)
            {
                int idx = rnd.Next(0, 2000000000);
                listType[idx] = rnd.Next();
            }

            sw.Stop();

            Console.WriteLine("Insertion in MyList<int> took " + sw.Elapsed.TotalSeconds + " seconds");

            sw.Reset();
            sw.Start();
            Console.WriteLine("Inserting into CoolType<int>");

            for (int i = 0; i < 1000000; i++)
            {
                int idx = rnd.Next(0, int.MaxValue);
                coolType[idx] = rnd.Next();
            }

            sw.Stop();

            Console.WriteLine("Insertion in MyList<int> took " + sw.Elapsed.TotalSeconds + " seconds");

            sw.Reset();

            Console.WriteLine("Looking up 1,000,000 random elements in MyList<int>");

            sw.Start();
            int x = 0;

            for (int i = 0; i < 10000000; i++)
            {
                int idx = rnd.Next(0, 2000000000);
                x = listType[idx];
            }

            sw.Stop();
            Console.WriteLine("Looking up 1,000,000 random elements in MyList<int> took " + sw.Elapsed.TotalSeconds + " seconds");

            sw.Reset();

            Console.WriteLine("Looking up 1,000,000 random elements in MyList<int>");

            sw.Start();

            for (int i = 0; i < 10000000; i++)
            {
                int idx = rnd.Next(0, int.MaxValue);
                bool found = coolType.TryGetValue(idx, out x);
            }

            sw.Stop();
            Console.WriteLine("Looking up 1,000,000 random elements in CoolType<int> took " + sw.Elapsed.TotalSeconds + " seconds");

            Console.ReadLine();
        }

    }

    public class MyCoolType<T> : Dictionary<int, T> { }

    public class MyList<T> : List<T>
    {
        public T this[int i]
        {
            get
            {
                while (i >= this.Count) this.Add(default(T));
                return base[i];
            }
            set
            {
                while (i >= this.Count) this.Add(default(T));
                base[i] = value;
            }
        }
    }
}