如何让任务在C＃4.0中睡眠（或延迟）？

Question

.NET 4.5中有Task.Delay

如何在.NET 4.0中执行相同操作？

Answer 1

可以使用Timer创建Delay方法在4.0：

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; 
} 

Answer 2

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; 
    } 
} 

从部分How to implement Task.Delay in 4.0

Answer 3

您也可以下载Visual Studio Async CTP和使用TaskEx.Delay

Answer 4

使用来自NuGet的Microsoft.Bcl.Async包装，它有TaskEx.Delay。

Answer 5

以下是可取消Task.Delay实现的代码和示例工具。你是在Delay方法：

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; 
     } 
    } 
} 

Answer 6

在很多情况下，一个纯粹的AutoResetEvent比Thread.sleep（）方法可能会更好...感兴趣

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

希望它有助于

Answer 7

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(); 
     } 
    } 

Answer 8

这里有一个简洁的，基于定时器的实现与适当的清理：

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

要在.NET 4.0上使用此代码，您需要使用Microsoft.Bcl.Async NuGet包。

Answer 9

从这个answer扩展思路：

new AutoResetEvent(false).WaitOne(1000);