.NET Task 实例可以在运行期间超出范围吗?

Can .NET Task instances go out of scope during run?(.NET Task 实例可以在运行期间超出范围吗?)

问题描述

如果我在方法中有以下代码块(使用 .NET 4 和任务并行库):

If I have the following block of code in a method (using .NET 4 and the Task Parallel Library):

var task = new Task(() => DoSomethingLongRunning());
task.Start();

然后方法返回，该任务会超出范围并被垃圾收集，还是会运行完成?我没有注意到 GCing 有任何问题，但我想确保我没有为 GC 设置竞争条件.

and the method returns, will that task go out of scope and be garbage collected, or will it run to completion? I haven't noticed any issues with GCing, but want to make sure I'm not setting myself up for a race condition with the GC.

推荐答案

更新:

在我回答了这个问题之后(很久以前！)，我发现任务总是运行到完成是不正确的 - 有一个小的，比如说角落"的情况，任务可能无法完成.

After I answered this question (a long time ago!) I found out that it's not true that Tasks will always run to completion - there's a small, let's say "corner" case, where tasks may not finish.

原因是这样的:正如我之前回答的那样，任务本质上是线程；但它们是 background 线程.当所有前台线程完成时，后台线程会自动中止.因此，如果您对任务不做任何事情并且程序结束，则任务可能无法完成.

The reason for that is this: As I have answered previously, Tasks are essentially threads; but they are background threads. Background threads are automatically aborted when all foreground threads finish. So, if you don't do anything with the task and the program ends, there's a chance the task won't complete.

您应该始终等待任务.更多信息可以在 Jon 给我的优秀答案上找到.

You should always await on tasks. More information can be found on the excellent answer Jon gave me.

原文:

任务被调度到 ThreadPool，这意味着它们本质上是线程¹(实际上，它们封装了线程).

Task are scheduled to the ThreadPool, meaning that they are essentially threads¹ (actually, they encapsulate threads).

来自 线程文档:

没有必要保留一旦你引用一个 Thread 对象已经启动线程.线程继续执行直到线程程序完成.

It is not necessary to retain a reference to a Thread object once you have started the thread. The thread continues to execute until the thread procedure is complete.

所以，不，没有必要保留对它的引用.

So, no, there is no need to retain a reference to it.

此外，文档 指出创建任务是使用它的工厂:

Also, the documentation states that the preferred way to create a Task is to use it's factory:

您也可以使用 StartNew 方法一次创建和启动一项任务手术.这是首选方式创建并启动任务(如果创建)和调度不必是分开(...)

You can also use the StartNew method to create and start a task in one operation. This is the preferred way to create and start tasks if creation and scheduling do not have to be separated (...)

希望对你有帮助.

¹ 根据文档:

一个任务代表一个异步操作，并且在某些方面它类似于创建一个新线程或 ThreadPool 工作项，但在更高层次的抽象.

A task represents an asynchronous operation, and in some ways it resembles the creation of a new thread or ThreadPool work item, but at a higher level of abstraction.

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