Answer to http://stackoverflow.com/q/10432494/61061: observing the death of client threads

ThreadMonitor.cs

using System;
using System.Threading;

namespace ThreadingTest
{
    public class ThreadMonitor
    {
        public static event Action<int> Finalized = delegate { };
        private readonly int m_threadId = Thread.CurrentThread.ManagedThreadId;

        ~ThreadMonitor()
        {
            Finalized(ThreadId);
        }

        public int ThreadId
        {
            get { return m_threadId; }
        }
    }

    public static class Test
    {
        private readonly static ThreadLocal<ThreadMonitor> s_threadMonitor = 
            new ThreadLocal<ThreadMonitor>(() => new ThreadMonitor());

        public static void Main()
        {
            ThreadMonitor.Finalized += i => Console.WriteLine("thread {0} closed", i);
            var thread = new Thread(() =>
            {
                var threadMonitor = s_threadMonitor.Value;
                Console.WriteLine("start work on thread {0}", threadMonitor.ThreadId);
                Thread.Sleep(1000);
                Console.WriteLine("end work on thread {0}", threadMonitor.ThreadId);
            });
            thread.Start();
            thread.Join();

            // wait for GC to collect and finalize everything
            GC.GetTotalMemory(forceFullCollection: true);

            Console.ReadLine();
        }
    }
}