using System;

using System.Collections.Generic;

using System.Diagnostics;

using System.Threading;

using System.Threading.Tasks;

​

class Program

{

    static async Task Main()

    {

        var stopwatch = Stopwatch.StartNew();

        Thread workerThread = null;

        List<(string, long, System.Threading.ThreadState)> entries = new();

        Task<Task> taskTask = Task.Factory.StartNew(async () =>

        {

            workerThread = Thread.CurrentThread;

            entries.Add(("A", stopwatch.ElapsedMilliseconds, workerThread.ThreadState));

            await Task.Delay(500);

            entries.Add(("D", stopwatch.ElapsedMilliseconds, workerThread.ThreadState));

        }, default, TaskCreationOptions.LongRunning, TaskScheduler.Default);

​

        taskTask.Wait();

        entries.Add(("B", stopwatch.ElapsedMilliseconds, workerThread.ThreadState));

​

        workerThread.Join();

        entries.Add(("C", stopwatch.ElapsedMilliseconds, workerThread.ThreadState));

​

        await taskTask.Unwrap();

        entries.Add(("E", stopwatch.ElapsedMilliseconds, workerThread.ThreadState));

​

        foreach (var (title, elapsed, state) in entries)

            Console.WriteLine($"{title } after {elapsed,3} msec worker thread is {state}");

    }

}

​