C# Task.Delay()和Thread.Sleep()有什么区别？

Posted 2022-09-07 dotNET跨平台

     很多时候我们需要做一段延时处理，就直接Thread.Sleep(n)处理了，但实际上延时也可以用Task.Delay(n)，那二者之间有没有区别呢？

我们先来看一个案例：

using System;
using System.Threading;
using System.Threading.Tasks;


namespace ConsoleApp22

    class Program
    
        static void Main(string[] args)
        
            //Good writing
            Task.Run(async () =>
            
                int delayTimeCount = 0;
                while (true)
                
                    Console.WriteLine($"Delay第++delayTimeCount秒");
                    await Task.Delay(1000);
                
            );


            //Bad writing
            Task.Run(() =>
            
                int sleepTimeCount = 0;
                while (true)
                
                    Console.WriteLine($"Thread++sleepTimeCount秒");
                    Thread.Sleep(1000);
                
            );


            Console.ReadKey();
        
    

运行结果：

区别：

①.Thread.Sleep()是同步延迟，既然是同步的，自然会阻塞当前线程；Task.Delay()是异步延迟，则不会阻塞线程；
②.Thread.Sleep()不能中途取消，Task.Delay()可以，delay有四个重载方法，需要取消的话，可以调用Delay(int millisecondsDelay, CancellationToken cancellationToken)这个方法；

//
        // 摘要:
        //     Creates a task that completes after a specified number of milliseconds.
        //
        // 参数:
        //   millisecondsDelay:
        //     The number of milliseconds to wait before completing the returned task, or -1
        //     to wait indefinitely.
        //
        // 返回结果:
        //     A task that represents the time delay.
        //
        // 异常:
        //   T:System.ArgumentOutOfRangeException:
        //     The millisecondsDelay argument is less than -1.
        public static Task Delay(int millisecondsDelay);
        //
        // 摘要:
        //     Creates a cancellable task that completes after a specified number of milliseconds.
        //
        // 参数:
        //   millisecondsDelay:
        //     The number of milliseconds to wait before completing the returned task, or -1
        //     to wait indefinitely.
        //
        //   cancellationToken:
        //     A cancellation token to observe while waiting for the task to complete.
        //
        // 返回结果:
        //     A task that represents the time delay.
        //
        // 异常:
        //   T:System.ArgumentOutOfRangeException:
        //     The millisecondsDelay argument is less than -1.
        //
        //   T:System.Threading.Tasks.TaskCanceledException:
        //     The task has been canceled.
        //
        //   T:System.ObjectDisposedException:
        //     The provided cancellationToken has already been disposed.
        public static Task Delay(int millisecondsDelay, CancellationToken cancellationToken);
        //
        // 摘要:
        //     Creates a task that completes after a specified time interval.
        //
        // 参数:
        //   delay:
        //     The time span to wait before completing the returned task, or TimeSpan.FromMilliseconds(-1)
        //     to wait indefinitely.
        //
        // 返回结果:
        //     A task that represents the time delay.
        //
        // 异常:
        //   T:System.ArgumentOutOfRangeException:
        //     delay represents a negative time interval other than TimeSpan.FromMilliseconds(-1).
        //     -or- The delay argument's System.TimeSpan.TotalMilliseconds property is greater
        //     than System.Int32.MaxValue.
        public static Task Delay(TimeSpan delay);
        //
        // 摘要:
        //     Creates a cancellable task that completes after a specified time interval.
        //
        // 参数:
        //   delay:
        //     The time span to wait before completing the returned task, or TimeSpan.FromMilliseconds(-1)
        //     to wait indefinitely.
        //
        //   cancellationToken:
        //     A cancellation token to observe while waiting for the task to complete.
        //
        // 返回结果:
        //     A task that represents the time delay.
        //
        // 异常:
        //   T:System.ArgumentOutOfRangeException:
        //     delay represents a negative time interval other than TimeSpan.FromMilliseconds(-1).
        //     -or- The delay argument's System.TimeSpan.TotalMilliseconds property is greater
        //     than System.Int32.MaxValue.
        //
        //   T:System.Threading.Tasks.TaskCanceledException:
        //     The task has been canceled.
        //
        //   T:System.ObjectDisposedException:
        //     The provided cancellationToken has already been disposed.
        public static Task Delay(TimeSpan delay, CancellationToken cancellationToken);

③在异步代码中通常使用await关键字调用Task.Delay()，而不是Thread.Sleep()；