如何编写C＃5异步？ [英] How to write C# 5 async?

问题描述

我有以下情形：结果
当命令被输入（用于测试，这是一个控制台应用程序，当它准备好了，我希望这将是一个WebService）我执行一些code，并且需要进一步的用户输入的时候，我回到命令间$ P马上$ PTER。当新的输入给定，我要处理，从我离开那里重新开始。这听起来这么像C＃5异步等待模式，我决定试一试。
我在想这个问题：

I have the following scenario:
When a command is inputted (for test, it's a console application, when it's ready, I hope it will be a WebService) I execute some code, and when further user input is needed, I return to the command interpreter immediately. When the new input is given, I want processing to resume from where I left it. That sounds so much like c#5 async-await pattern, that I decided to give it a try. I was thinking about this:

public void CommandParser()
{
   while(true)
   { 
      string s = Console.ReadLine();
      if (s == "do_something")
         Execute();
      else if (s == "give_parameters")
         SetParameters();
      //... 
   }
}
MySettings input;
public async void Execute()
{
  //do stuff here
  MyResult result = null
  if (/*input needed*/){
     input = new MySetting();
     result = await input.Calculate();
  }
  else { /* fill result synchronously*/}
  //do something with result here

}

public void SetParameters()
{
   if (input!=null)
      input.UseThis("something"); //now it can return from await
}

现在我的问题是，如何写MySettings.Calculate和MySettings.UseThis？如何从第一返回任务，以及如何从第二信号readyness？我试过许多工厂方法的任务，但我不能找到合适的人！请帮助！

Now my question is, how to write MySettings.Calculate and MySettings.UseThis? How to return a Task from the first and how to signal readyness from the second? I've tried with many factory methods for Task, but I can't find the right one! Please help!

推荐答案

一种选择是使用的 TaskCompletionSource＆LT; T＆GT; 。这将建立一个任务你，你可以叫的setResult 或 SetException 的来源，这将标志着任务适当。

One option is to use TaskCompletionSource<T>. That will build a task for you, and you can call SetResult or SetException on the source, which will signal the task appropriately.

这是我用什么来<一个href=\"http://msmvps.com/blogs/jon_skeet/archive/2011/05/15/eduasync-part-4-filling-in-asynctaskmethodbuilder-lt-t-gt.aspx\"相对=nofollow>实施 AsyncTaskMethodBuilder＆LT; T＆GT; 为Eduasync - 所以你可以看一下的例子

That's what I've used to implement AsyncTaskMethodBuilder<T> for Eduasync - so you can look at that for an example.

您会需要或者建立 TaskCompletionSource 事前或执行一些其他的协调，以便 input.Calculate 和 UseThis 都知道同一个对象 - 但计算将只返回 completionSource.Task 和 UseThis 会叫 completionSource.SetResult 。

You'd need to either set up the TaskCompletionSource beforehand or perform some other coordination so that input.Calculate and UseThis both know about the same object - but then Calculate would just return completionSource.Task, and UseThis would call completionSource.SetResult.

记住，当你调用的setResult ，异步方法会继续下去在不同的线程池线程，如果你使用一个控制台应用程序（或Web服务） - 所以你无疑是想建立一个的不同的的 TaskCompletionSource 的主循环再使用，为下一轮，因为它是。

Bear in mind that when you call SetResult, the async method will keep going on a different thread-pool thread if you're using a console app (or web service) - so you'd no doubt want to create a different TaskCompletionSource for the main loop to then use for the next round, as it were.

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