在循环内启动任务：如何传递可以在循环内更改的值？

发布于 2024-10-27 01:50:04 字数 368 浏览 1 评论 0原文

我正在尝试在 while 循环内使用 TPL，并且需要将一些值传递给任务，然后这些值会更改为循环。例如，这里显示了一个索引递增的示例（必须在请求创建任务的行之后）：

int index = 0;
Task[] tasks;
while(/*condition*/)
{
    tasks[index] = Task.Factory.StartNew(() => DoJob(index));
    index++;
}

但是它当然不起作用，因为索引值可以在任务开始之前递增。一个可能的解决方案可能是还传递一个 WaitHandle，在增加索引之前等待，并且必须将其发送到 DoJob 方法，但在我看来这并不是一个很好的解决方案。还有其他想法吗？

原文

I'm trying to use TPL inside a while loop and I need to pass to the task some values that then changes into the loop. For instance, here it is shown an example with an index that is incremented (necessarily after the line in which the task creation is requested):

int index = 0;
Task[] tasks;
while(/*condition*/)
{
    tasks[index] = Task.Factory.StartNew(() => DoJob(index));
    index++;
}

But of course it does not work, since the index value can be incremented before the task start. A possible solution could be to pass also a WaitHandle on which waiting before incrementing the index and that has to be signalled into the DoJob method, but it doesn't seem to me a really good solution. Any other idea?

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一抹微笑 2024-11-03 01:50:04

将值分配给循环内的临时变量：

int index = 0;
Task[] tasks;
while(/*condition*/)
{
    int value = index;
    tasks[index] = Task.Factory.StartNew(() => DoJob(value));
    index++;
}

这样，每个任务都将拥有自己的 index 在 while 循环迭代期间所拥有的值副本，其中调用到 StartNew 已完成。

Assign the value to a temporary variable inside the loop:

int index = 0;
Task[] tasks;
while(/*condition*/)
{
    int value = index;
    tasks[index] = Task.Factory.StartNew(() => DoJob(value));
    index++;
}

That way each task will have its own copy of the value that index had during the iteration of the while loop in which call to StartNew was made.

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