C# .Net - 如何让应用程序等到库中创建的所有线程都完成

Question

我正在尝试创建一个日志库，并且在调用应用程序关闭之前一切都很好。当调用应用程序关闭时，任何未完成的线程都会被杀死并且特定的日志会丢失。

到目前为止，应用程序甚至在前 10 个线程完成之前就退出了。我需要有关如何让应用程序等到库创建的所有线程都完成的帮助。

注意： 我得到的要求是这样的。修改只能在“Logging”类中，因为这将是一个库并将提供给最终用户。必须在应用程序关闭期间处理日志记录问题。这就是我现在遇到问题的地方。

另外一种解决方案，如在日志记录类中创建一个事件以触发所有日志记录完成，并要求用户在该事件上调用应用程序退出是可能的，但我试图避免这种情况，因为它给最终用户增加了负担并增加了复杂性用于实施。他们有可能会跳过它，这是我不想要的。我正在寻找一个解决方案，比如用户应该执行 'Logging.AddException(....)' 然后忘记它。

请帮忙。如果您不清楚这个想法，请提供 cmets。

这是您可以放入控制台应用程序的完整代码摘要。 注意：在 CASE 1 和 CASE 2 中寻找 cmets。

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace MultithreadKeepAlive
{
class Program
{
    static void Main(string[] args)
    {
        LogLoadTest();
        Logging.AddExceptionEntryAsync(new Exception("Last Exception"));

        /*
         * USE CASE 1: Enable the below lines and you will see how long it is supposed to take.
         * Notice that currentDomain_ProcessExit will not trigger if below gets uncommented
         */
        //Console.WriteLine("Main thread wait override");
        //Console.ReadLine();
    }

    static void LogLoadTest()
    {
        //In real world this will be called from any place of application like startup or just after application shutdown is initiated.
        //: NOTICE: Unlike the sample here, this will never be on loop and I am not looking for handling multithreads in this class.
        //      That responsibility I am planning to assign to Logging class.
        // AND ALSO the class Logging is going to be in a seperate signed assembly where user of this class ('Program') should not worry about multithreads.
        Task t;
        for (int i = 0; i < 40; i++)
        {
           t =  Logging.AddExceptionEntryAsync(new Exception("Hello Exception " + i), "Header info" + i);
        }
    }
}

public class Logging
{
    static List<Task> tasks = new List<Task>();

    static AppDomain currentDomain;
    static Logging()
    {
        currentDomain = AppDomain.CurrentDomain;
        currentDomain.ProcessExit += currentDomain_ProcessExit;
    }

    public static async Task AddExceptionEntryAsync(Exception ex, string header = "")
    {
        Task t = Task.Factory.StartNew(() => AddExceptionEntry(ex, header));
        tasks.Add(t);
        await t;
    }

    public static void AddExceptionEntry(Exception ex, string header)
    {
        /* Exception processing and write to file or DB. This might endup in file locks or 
         * network or any other cases where it will take delays from 1 sec to 5 minutes. */
        Thread.Sleep(new Random().Next(1, 1000));
        Console.WriteLine(ex.Message);
    }

    static void currentDomain_ProcessExit(object sender, EventArgs e)
    {
            Console.WriteLine("Application shutdown triggerd just now.");
            Process.GetCurrentProcess().WaitForExit();    //1st attempt.
            //Task.WaitAll(tasks.ToArray()); //2nd attempt
            while (tasks.Any(t => !t.IsCompleted)) //3rd attempt.
            {
            }
            /* USE CASE 2: IF WORKING GOOD, THIS WILL BE DISPLAYED IN CONSOLE AS LAST 
             * MESSAGE OF APPLICATION AND WILL WAIT FOR USER. THIS IS NOT WORKING NOW.*/
            Console.WriteLine("All complete"); //this message should show up if this work properly
            Console.ReadLine(); //for testing purpose wait for input from user after every thread is complete. Check all 40 threads are in console.
    }
}

}

Answer 1

你可以试试

Task.WaitAll(tasks);

这会等待所有提供的 Task 对象完成执行。

更新：使用异步/等待

通过 async 和 await，我们形式化并阐明了异步、非阻塞方法是如何开始和结束的。异步方法只能返回 void 或 Task。

static void Main()
{
// Create task and start it.
// ... Wait for it to complete.
Task task = new Task(AsyncMethod);
task.Start();
task.Wait();
}

public static async void AsyncMethod(){
await AnotherMehod();}

static async Task AnotherMehod() { //TODO}

Answer 2

到目前为止，我自己找到了解决方法。

    /// <summary>
    /// Makes the current thread Wait until any of the pending messages/Exceptions/Logs are completly written into respective sources.
    /// Call this method before application is shutdown to make sure all logs are saved properly.
    /// </summary>
    public static void WaitForLogComplete()
    {
        Task.WaitAll(tasks.Values.ToArray());
    }

Answer 3

第 1 步：如果您不希望调度程序参与进来，请考虑更改为 Task.Run()。我还假设您想等到所有异步任务完成。

public static AddExceptionEntry(Exception ex, string header = "")
{
    Task t = Task.Factory.StartNew(() => AddExceptionEntry(ex, header));
    tasks.Add(t);

    WaitForExecutionAsync().ConfigureAwait(true);
}

public static async Task WaitForExecutionAsync()
{
    if(tasks.Count >0) 
        await Task.WhenAll(tasks.ToArray());
    // Raise Event.
}

要阻止只需调用它来运行同步与异步：

WaitForExecution().GetAwaiter().GetResult();