AsyncLocal issue.cs

using System;
using System.Threading;

namespace ConsoleApplication
{
    internal class Program
    {
        const int UnexpectedTimeoutMilliseconds = 30 * 1000;

        public static void Main(string[] args)
        {
            var asyncLocal = new AsyncLocal<int>();
            asyncLocal.Value = 1;

            var obj = new object();
            var registerWaitEvent = new AutoResetEvent(false);
            var threadDone = new AutoResetEvent(false);
            RegisteredWaitHandle registeredWaitHandle = null;
            Exception backgroundEx = null;
            int backgroundAsyncLocalValue = 0;

            Action<bool, Action> commonBackgroundTest =
                (isRegisteredWaitCallback, test) =>
                {
                    try
                    {
                        if (isRegisteredWaitCallback)
                        {
                            RegisteredWaitHandle toUnregister = registeredWaitHandle;
                            registeredWaitHandle = null;
                            toUnregister.Unregister(threadDone);
                        }
                        test();
                        backgroundAsyncLocalValue = asyncLocal.Value;
                    }
                    catch (Exception ex)
                    {
                        backgroundEx = ex;
                    }
                    finally
                    {
                        if (!isRegisteredWaitCallback)
                        {
                            threadDone.Set();
                        }
                    }
                };
            Action<bool> waitForBackgroundWork =
                isWaitForRegisteredWaitCallback =>
                {
                    if (isWaitForRegisteredWaitCallback)
                    {
                        registerWaitEvent.Set();
                    }
                    threadDone.WaitOne(30 * 1000);
                };

            ThreadPool.QueueUserWorkItem(state => commonBackgroundTest(false, () =>{}), obj);
            waitForBackgroundWork(false);

            ThreadPool.UnsafeQueueUserWorkItem(state => commonBackgroundTest(false, () =>{}), obj);
            waitForBackgroundWork(false);

            registeredWaitHandle =
                ThreadPool.RegisterWaitForSingleObject(registerWaitEvent,
                    (state, timedOut) => commonBackgroundTest(true, () => {}),
                    obj, UnexpectedTimeoutMilliseconds, false);
            waitForBackgroundWork(true);

            registeredWaitHandle =
                ThreadPool.UnsafeRegisterWaitForSingleObject(registerWaitEvent, 
                    (state, timedOut) => commonBackgroundTest(true, () => {}),
                    obj, UnexpectedTimeoutMilliseconds, false);
            waitForBackgroundWork(true);
            Console.WriteLine("Should be 0: " + backgroundAsyncLocalValue);
            //.NET: 1
            //Mono: 0
        }
    }
}