如何等待任务的完成及其继续？

Question

我学习以书本为基础的线程。

我想等待我的任务及其继续进行。但是我在“ BLEEEEEEEEEEEEEEEP ” 之前看到“按任意键退出... ”消息（请查看我的代码注释）。为什么会发生，如何解决？

我知道我可以使用两个任务并将其Task.Wait()用于每个任务，但是如果我需要对延续对象执行相同的操作怎么办？

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

OnCompleted事件是在您不等待的其他线程上触发的。您可以使用以下构造：

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

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

awaiter.GetResult();

在这种情况下，act1将使用第一个任务执行该任务，当该任务完成时，它将继续执行act2。在这种情况下，等待者将等待两者均完成。