How to wait a finish of the task and its continuation?

Question

I learn to work with the threads on the base of a book.

I want to wait while my task and its continuation are working. But I see the "Press any key for exit... " message before " BLEEEEEEEEEEEEEEEP " (look the comments of my code, please). Why does it happen and how can I fix it?

I know that I can use two tasks and to use Task.Wait() for each of them, but what if I need to do the same for the continuation object ?

using System;
using System.Threading;
using System.Threading.Tasks;

namespace Bushman.Sandbox.Threads {
    class Program {
        static void Main(string[] args) {
            Console.Title = "Threads";

            try {
                // The main work
                Action act1 = () => {
                    for (int i = 0; i < 10; i++) {

                        int id = Thread.CurrentThread
                        .ManagedThreadId;

                        Console.WriteLine(
                            "bleep. Thread Id: {0}",
                            id.ToString());
                    }
                };

                // This operation is to be done when the main 
                // work will be finished.
                Action act2 = () => {

                    int id = Thread.CurrentThread
                        .ManagedThreadId;

                    Console.WriteLine(
                        "bleep. Thread Id: {0}",
                        id.ToString());

                    Console.WriteLine(
                        "BLEEEEEEEEEEEEEEEP. Thread Id: {0}",
                            id.ToString());
                };

                Task task = new Task(act1);
                var awaiter = task.GetAwaiter();
                awaiter.OnCompleted(act2);

                Console.WriteLine("Work started...");
                task.Start();

                // TODO: wait while both actions will be done

                task.Wait(); // it doesn't work as I expected

                // it doesn't work as I expected too...
                awaiter.GetResult();
            }
            catch (Exception ex) {
                Console.ForegroundColor = ConsoleColor.Red;
                Console.WriteLine(ex.Message);
                Console.ResetColor();
            }

            Console.WriteLine("Press any key for exit...");
            Console.ReadKey();
        }
    }
}

Answer 1

The OnCompleted event is triggered on a different thread that you are not waiting for. You could use the following construct:

Task task = new Task(act1);
var awaiter = task.ContinueWith(x => act2()).GetAwaiter();
task.Start();

Console.WriteLine("Work started...");

awaiter.GetResult();

In this case act1 will be executed using the first task and when this task is completed it will continue with act2 . The awaiter in this case will wait for both to complete.