Why my example does not work on thread pool testing?

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Threading;
using System.Windows.Forms;
using System.Diagnostics;

namespace ThreadPool01
{
    class Program
    {
        static void Main(string[] args)
        {
            Program p = new Program();

            Console.WriteLine("testing thread pool numbers:");
            p.CallFoo30AsyncTimes();
            Console.ReadKey();
        }

        private void CallFoo30AsyncTimes()
        {
            // create a delegate of MethodInvoker
            // poiting to our Foo function.
            MethodInvoker simpleDelegate =  new MethodInvoker(Foo);

            // Calling Foo Async 30 times.
            for (int i = 0; i < 30; i++)
            {
                // call Foo()
                simpleDelegate.BeginInvoke(null, null);
            }
        }

        private void Foo()
        {
            int intAvailableThreads, intAvailableIoAsynThreds;

            // ask the number of avaialbe threads on the pool,
            //we really only care about the first parameter.
            ThreadPool.GetAvailableThreads(out intAvailableThreads, out intAvailableIoAsynThreds);

            // build a message to log
            string strMessage =
                String.Format(@"Is Thread Pool: {0}, Thread Id: {1} Free Threads {2}",
                    Thread.CurrentThread.IsThreadPoolThread.ToString(), Thread.CurrentThread.GetHashCode(), intAvailableThreads);

            // check if the thread is on the thread pool.
            Trace.WriteLine(strMessage);

            // create a delay...
            Thread.Sleep(3000);

            return;
        }
    }
}