[英]How do I fallback to the Default TaskScheduler from a custom TaskScheduler
Let's say I want to create a custom TaskScheduler, but inside it, fall back to the default if some criteria do not apply. 假设我想创建一个自定义TaskScheduler,但在其中,如果某些条件不适用,则回退到默认值。 How do I do that? 我怎么做?
Eg 例如
protected override void QueueTask(Task task) {
if (/* some condition */) {
/* schedule task manually, does not matter */
}
/* queue task on default -- how? */
}
protected override IEnumerable<Task> GetScheduledTasks() {
return Enumerable.Concat(/* my tasks */, /* tasks from default -- how? */);
}
I don't think you can (or should) do this, even if you resorted to reflection hacks. 我不认为你可以(或应该)这样做,即使你使用反射黑客。 In theory, you'd need to derive your custom TaskScheduler
from existing non-abstract task scheduler, eg ThreadPoolTaskScheduler
. 理论上,您需要从现有的非抽象任务调度程序派生自定义TaskScheduler
,例如ThreadPoolTaskScheduler
。
However, you can't because all non-abstract implementations of TaskScheduler
in TPL are either private
or internal
. 但是,你不能,因为TPL中TaskScheduler
所有非抽象实现都是private
或internal
。
In case with TaskScheduler.QueueTask
, it might be tempting to simply forward the call to Task.Start
: 对于TaskScheduler.QueueTask
,可能很容易将调用转发到Task.Start
:
protected override void QueueTask(Task task) {
if (/* some condition */) {
/* schedule task manually, does not matter */
}
/* queue task on default -- how? */
task.Start(TaskScheduler.Default);
}
However, you can not do this, either. 但是,你也不能这样做。 The implementation of Task.Start
calls TaskScheduler.QueueTask
internally, which would result in infinite recursion. Task.Start
的实现在Task.Start
调用TaskScheduler.QueueTask
,这将导致无限递归。
Moreover, the Task
object stores a reference to the task scheduler inside Task.Start
. 此外, Task
对象在Task.Start
存储对任务调度程序的Task.Start
。 So, say, if you used reflection to call ThreadPoolTaskScheduler.QueueTask
, it would break the connection between the task and its task scheduler. 因此,如果您使用反射来调用ThreadPoolTaskScheduler.QueueTask
,它将破坏任务与其任务调度程序之间的连接。
So, there's a good reason that QueueTask
, GetScheduledTasks
and some other methods of TaskScheduler
are declared as protected
. 因此,有一个很好的理由将QueueTask
, GetScheduledTasks
和TaskScheduler
其他一些方法声明为protected
。 If you're into implementing a custom task scheduler, you have to provide the full implementation. 如果您要实现自定义任务计划程序,则必须提供完整的实现。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.