在WaitHandle.WaitOne方法上使用的exitContext是什么

using System;
using System.Threading;

class Program
{
    static void Main()
    {
        AutoResetEvent autoEvent = new AutoResetEvent(false);

        ThreadPool.QueueUserWorkItem(delegate
        {
            Console.WriteLine("Worker thread started.");
            Thread.Sleep(1000);
            Console.WriteLine("Worker thread signaling the event.");
            autoEvent.Set();
        });

        Console.WriteLine("Main thread waiting for event...");
        autoEvent.WaitOne(TimeSpan.FromSeconds(5), true);
        Console.WriteLine("Main thread received event signal.");
    }
}