。继续启动任务完成之前， [英] .Continue starts before task is completed

问题描述

我有以下的code在C＃中，VS2012，WPF 4.5。 我的期望是如此， .ContinueWith 会后，任务完成完全执行（这是一个延续的全部目的，是不是？）。

I have the following code in C#, VS2012, WPF 4.5. My expectation would be that, .ContinueWith will be executed after the task has finished completely (that's a continuation's whole purpose, isn't it?).

这应该导致2的值 finalResult 。

int myTestInt = 0;

Task task = Task.Factory.StartNew(async () =>
{
   myTestInt = 1;
   await Task.Delay(TimeSpan.FromSeconds(6));
   myTestInt = 2;

}).ContinueWith(_ =>
   {
      int finalResult = myTestInt;
   });

其实， finalResult 分配值1来代替。因此，它似乎是继续开始在等待语句了。

In fact, finalResult is assigned a value of 1 instead. So it seems like the continuation is started on the await statement already.

这是预期的行为？我失去了一些东西呢？我不能靠 ContinueWith 启动后的任务已经彻底完蛋了？

Is this the intended behaviour? Am I missing something here? Can't I rely on ContinueWithto start after a task has completely finished?

更新：

贾斯汀的回答只是激励我检查以下内容：

Justin's answer just inspired me to check the following:

int myTestInt = 0;
Task task=Task.Factory.StartNew(async () =>
{
   myTestInt = 1;
   await Task.Delay(TimeSpan.FromSeconds(6));
   myTestInt = 2;
});

task.Wait();
int result2 = myTestInt;

finalResult仍然设置为1。请问有没有办法可靠地等待包含等待 s到完成？

推荐答案

当你传递一个异步授人以 Task.Factory.StartNew ，返回工作仅重presents该委托的第一部分（直到一次等待件事情是不是已经完成）。

When you pass an async delegate to Task.Factory.StartNew, the returned Task only represents the first portion of that delegate (up until the time it awaits something that is not already completed).

不过，如果你传递一个异步委托给新的 Task.Run 方法（该方法被列入此原因），则返回工作重presents整个委托。所以，你可以使用 ContinueWith 如您所愿。 （虽然等待通常比一个更好的选择 ContinueWith ）。

However, if you pass an async delegate to the new Task.Run method (which was included for this reason), the returned Task represents the entire delegate. So you can use ContinueWith as you expect. (Although await is usually a better option than ContinueWith).

有关 StartNew VS 运行的详细信息，请参阅斯蒂芬Toub关于这个专题的的帖子。

For more information on StartNew vs Run, see Stephen Toub's post on the topic.

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