为什么我在这里看到ConfigureAwait（false）和ConfigureAwait（true）没有区别？

Question

我正试图为我在async - await上做的报告创建一个概念验证。

我由代码

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

public class Program 
{ 
    static async Task CreateATaskThatPrintsWhichThread() 
    { 
     Console.WriteLine("Thread on line right before the bottom await = {0}", Thread.CurrentThread.ManagedThreadId); 
     await Task.Run(() => 
     { 
      Task.Delay(500); 
      Console.WriteLine("Thread on line inside bottom task action = {0}", Thread.CurrentThread.ManagedThreadId);       
     }); 
     Console.WriteLine("Thread on line right before the bottom await = {0}", Thread.CurrentThread.ManagedThreadId); 
    } 

    public static void Main() 
    { 
     Task.Run(async() => 
     { 
      Console.WriteLine("Thread on line right before the bottom await = {0}", Thread.CurrentThread.ManagedThreadId); 
      Task printStuff = CreateATaskThatPrintsWhichThread(); 
      printStuff.ConfigureAwait(true); 
      await printStuff; 
      Console.WriteLine("Thread on line right before the bottom await = {0}", Thread.CurrentThread.ManagedThreadId); 
     }).Wait(); 
    } 
} 

的样品片，其我反复上.NET小提琴运行，结果是散发性的：

Thread on line right before the bottom await = 14 
Thread on line right before the bottom await = 14 
Thread on line inside bottom task action = 28 
Thread on line right before the bottom await = 28 
Thread on line right before the bottom await = 28 


Thread on line right before the bottom await = 28 
Thread on line right before the bottom await = 28 
Thread on line inside bottom task action = 28 
Thread on line right before the bottom await = 28 
Thread on line right before the bottom await = 28 


Thread on line right before the bottom await = 28 
Thread on line right before the bottom await = 28 
Thread on line inside bottom task action = 53 
Thread on line right before the bottom await = 53 
Thread on line right before the bottom await = 28 

等等。当我更改为`printStuff.ConfigureAwait（false）;

Thread on line right before the bottom await = 99 
Thread on line right before the bottom await = 99 
Thread on line inside bottom task action = 87 
Thread on line right before the bottom await = 36 
Thread on line right before the bottom await = 99 

Thread on line right before the bottom await = 45 
Thread on line right before the bottom await = 45 
Thread on line inside bottom task action = 36 
Thread on line right before the bottom await = 36 
Thread on line right before the bottom await = 45 

Thread on line right before the bottom await = 25 
Thread on line right before the bottom await = 25 
Thread on line inside bottom task action = 12 
Thread on line right before the bottom await = 12 
Thread on line right before the bottom await = 25 

有人可以告诉我结果“应该”，或者可以帮助我在.NET小提琴上创建一个更好的例子吗？

（我也很困惑，因为我认为线内内Task.Run已基本保证是在后台线程上执行）

Answer 1

的意见涵盖了大部分的这一点，但因为没有答案，我认为你之后的答案是你错误地得出结论.ConfigureAwait(true)意味着在await之后，代码将继续与之前相同的线程。

这是真的在某些情况下，特别是那些具有某种形式的消息/调度器循环。在这些情况下，当预继续代码完成时，SynchronizationContext捕获的数据用于将请求发送回调度程序，以便在下一次能够时接收延续并在其线程上继续执行延续。该循环通常持续快速地旋转，为UI关注提供服务，并且一旦帖子被注册，它将使用其迭代中的一个来执行延续。

控制台应用程序没有这样的循环，也没有SynchronizationContext，所以执行continuation的任务被排队到线程池，任何可用的线程都会执行它。偶尔你会得到幸运，并最终得到与延续之前相同的线索，但那只是偶然。