如何在c# 4.0中让任务休眠(或延迟)

本文关键字：休眠 任务 延迟 | 更新日期: 2023-09-27 18:03:16

有任务。.NET 4.5中的延迟

如何在。net 4.0中做同样的事情?

如何在c# 4.0中让任务休眠(或延迟)

使用NuGet的Microsoft.Bcl.Async包，它有TaskEx.Delay .

您可以使用Timer在4.0中创建Delay方法:

public static Task Delay(double milliseconds)
{
    var tcs = new TaskCompletionSource<bool>();
    System.Timers.Timer timer = new System.Timers.Timer();
    timer.Elapsed+=(obj, args) =>
    {
        tcs.TrySetResult(true);
    };
    timer.Interval = milliseconds;
    timer.AutoReset = false;
    timer.Start();
    return tcs.Task;
}

using System;
using System.Threading;
using System.Threading.Tasks;
class Program
{
    static void Main()
    {
        Delay(2000).ContinueWith(_ => Console.WriteLine("Done"));
        Console.Read();
    }
    static Task Delay(int milliseconds)
    {
        var tcs = new TaskCompletionSource<object>();
        new Timer(_ => tcs.SetResult(null)).Change(milliseconds, -1);
        return tcs.Task;
    }
}

来自如何实现任务一节。4.0的延迟

下面是一个可取消任务的代码和样例。推迟实现。您可能对Delay方法感兴趣。:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace DelayImplementation
{
    class Program
    {
        static void Main(string[] args)
        {
            System.Threading.CancellationTokenSource tcs = new System.Threading.CancellationTokenSource();
            int id = 1;
            Console.WriteLine(string.Format("Starting new delay task {0}. This one will be cancelled.", id));
            Task delayTask = Delay(8000, tcs.Token);
            HandleTask(delayTask, id);
            System.Threading.Thread.Sleep(2000);
            tcs.Cancel();
            id = 2;
            System.Threading.CancellationTokenSource tcs2 = new System.Threading.CancellationTokenSource();
            Console.WriteLine(string.Format("Starting delay task {0}. This one will NOT be cancelled.", id));
            var delayTask2 = Delay(4000, tcs2.Token);
            HandleTask(delayTask2, id);
            System.Console.ReadLine();
        }
        private static void HandleTask(Task delayTask, int id)
        {
            delayTask.ContinueWith(p => Console.WriteLine(string.Format("Task {0} was cancelled.", id)), TaskContinuationOptions.OnlyOnCanceled);
            delayTask.ContinueWith(p => Console.WriteLine(string.Format("Task {0} was completed.", id)), TaskContinuationOptions.OnlyOnRanToCompletion);
        }
        static Task Delay(int delayTime, System.Threading.CancellationToken token)
        {
            TaskCompletionSource<object> tcs = new TaskCompletionSource<object>();
            if (delayTime < 0) throw new ArgumentOutOfRangeException("Delay time cannot be under 0");
            System.Threading.Timer timer = null;
            timer = new System.Threading.Timer(p =>
            {
                timer.Dispose(); //stop the timer
                tcs.TrySetResult(null); //timer expired, attempt to move task to the completed state.
            }, null, delayTime, System.Threading.Timeout.Infinite);
            token.Register(() =>
                {
                    timer.Dispose(); //stop the timer
                    tcs.TrySetCanceled(); //attempt to mode task to canceled state
                });
            return tcs.Task;
        }
    }
}

从这个答案延伸出这个想法:

new AutoResetEvent(false).WaitOne(1000);

您可以下载Visual Studio Async CTP并使用TaskEx。延迟

在很多情况下，一个纯粹的AutoResetEvent比Thread.Sleep()更好…

AutoResetEvent pause = new AutoResetEvent(false);
Task timeout = Task.Factory.StartNew(()=>{
pause.WaitOne(1000, true);
});

希望能有所帮助

    public static void DelayExecute(double delay, Action actionToExecute)
    {
        if (actionToExecute != null)
        {
            var timer = new DispatcherTimer
            {
                Interval = TimeSpan.FromMilliseconds(delay)
            };
            timer.Tick += (delegate
            {
                timer.Stop();
                actionToExecute();
            });
            timer.Start();
        }
    }

这是一个简洁的、基于计时器的实现，具有适当的清理功能:

var wait = new TaskCompletionSource<bool>();
using (new Timer(_ => wait.SetResult(false), null, delay, Timeout.Infinite))
    await wait.Task;

要在。net 4.0上使用这些代码，您需要Microsoft.Bcl.Async NuGet包。

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