for (int task = 0; task < 20; task++)
{
ThreadPool.QueueUserWorkItem(new WaitCallback(TaskCallBack), new object[] { filepath1, filepath2,
filepath3 });
}
public static void TaskCallBack(object state)
{
object[] array = state as object[];
string filea = Convert.ToString(array[0]);
string fileb = Convert.ToString(array[1]);
string filec = Convert.ToString(array[2]);
//something below
}
我希望等待主线程,直到所有线程完成其工作。请帮助
答案 0 :(得分:2)
处理此问题的最佳方法是使用Task.Run()
和Task.WhenAll()
,或使用Parallel.Invoke()
。
但是,如果您需要使用ThreadPool.QueueUserWorkItem
,则可以按以下方法解决此问题:
CountdownEvent
实例,该实例的初始化次数等于您要等待的线程数。 (在下面的示例代码中,此类称为ThreadData
。)TaskCallBack()
方法内,方法完成后调用CountdownEvent.Signal()
。CountdownEvent.Wait()
以等待所有线程完成。将所有内容放到可编译的控制台应用中:
using System;
using System.Threading;
namespace CoreConsole
{
public sealed class ThreadData
{
public ThreadData(CountdownEvent countdown, int index)
{
Countdown = countdown;
Index = index;
}
public CountdownEvent Countdown { get; }
public int Index { get; }
}
public static class Program
{
static void Main()
{
int n = 20;
var countdown = new CountdownEvent(n);
for (int task = 0; task < n; task++)
{
ThreadPool.QueueUserWorkItem(TaskCallBack, new ThreadData(countdown, task));
}
Console.WriteLine("Waiting for all threads to exit");
countdown.Wait();
Console.WriteLine("Waited for all threads to exit");
}
public static void TaskCallBack(object state)
{
var data = (ThreadData) state;
Console.WriteLine($"Thread {data.Index} is starting.");
Thread.Sleep(_rng.Next(2000, 10000));
data.Countdown.Signal();
Console.WriteLine($"Thread {data.Index} has finished.");
}
static readonly Random _rng = new Random(45698);
}
}
ThreadData.Index
属性仅用于标识Console.WriteLine()
调用中的每个线程。
注意:在实际代码中,即使线程引发异常,始终发出Countdown
事件也很重要-因此,您应该像这样将代码包装在try / final中:
public static void TaskCallBack(object state)
{
var data = (ThreadData)state;
try
{
// Do work here.
Console.WriteLine($"Thread {data.Index} is starting.");
Thread.Sleep(_rng.Next(2000, 10000));
Console.WriteLine($"Thread {data.Index} has finished.");
}
finally
{
data.Countdown.Signal();
}
}
答案 1 :(得分:1)
就像@Ackdari在他的评论中提到的那样,您可以使用 Task.Run 。但是您不需要 await 关键字。只需创建包含任务的集合,然后等待即可。
示例:
// Create a list that will hold the tasks
List<Task> tasks = new List<Task>;
// Create the tasks
for (int taskId = 0; taskId < 20; task++)
{
tasks.Add(Task.Run(() => { TaskCallBack(new object[] { filepath1, filepath2, filepath3 }); }));
}
// Wait for ALL tasks to complete
Task.WaitAll(tasks.ToArray());
这样,您还可以使用自己的方法,该方法将由任务运行。 示例:
public static void ReplaceWithABetterName(string[] filePaths)
{
string filea = filePaths[0);
string fileb = filePaths[1];
string filec = filePaths[2];
//do stuff
}