using System;

using System.Threading;

using System.Threading.Tasks;

using System.Collections.Generic;

​

public class Program

{

  static AsyncLocal<string> _asyncLocal = new AsyncLocal<string>();

  static async Task AsyncMain()

  {

    _asyncLocal.Value = "main";

    var t1 = AsyncTask("task 1", 200);

    Console.WriteLine("Called AsyncTask 1.");

    Console.WriteLine("   AsyncLocal value is '{0}'", _asyncLocal.Value);

    var t2 = AsyncTask("task 2", 100);

    Console.WriteLine("Called AsyncTask 2.");

    Console.WriteLine("   AsyncLocal value is '{0}'", _asyncLocal.Value);

​

    await Task.WhenAll(new List<Task>{ t1, t2 });

    Console.WriteLine("Awaited tasks.");

    Console.WriteLine("   AsyncLocal value is '{0}'", _asyncLocal.Value);

  }

​

  static async Task AsyncTask(string expectedValue, Int32 delay)

  {

    _asyncLocal.Value = expectedValue;

    await Task.Delay(delay);

    Console.WriteLine("In AsyncTask, expect '{0}'", expectedValue);

    Console.WriteLine("   AsyncLocal value is '{0}'", _asyncLocal.Value);

  }

​

  public static void Main()

  {

    AsyncMain().Wait();

  }

}