当两个线程都是WinForm时，在2个线程之间提高事件 [英] Raising an Event between 2 threads when neither thread is a WinForm

问题描述

我无法找到ac＃示例，显示如何在以下条件下提出跨线程事件：

假设我有1个事件和3个线程：

事件DoStuff

线程A - WinForm

线程B - 从线程A生成的线程进行一些处理。有功能Foo（）订阅DoStuff

线程C - 从线程B生成的线程进行一些子处理和提升事件DoStuff

现在我如何确保线程C中提升的事件在线程B而不是C或A内进行处理。

我运行的所有示例都提示使用Form / Control.Invloke，或者某种事情，我真的希望拥有任何Thread实际订阅的内容，而不仅仅是主表单线。

解决方案

将一个线程调用为具体其他线程是非常不平凡的。不可能任意中断线程并执行一些代码。这导致了可怕的重入问题。尝试通过使用信号量来保护这一点，可以保证会导致死锁。

目标线程必须合作，它必须是空闲的，而不是主动地突变状态的程序。一个常见的机制是线程安全的队列。事件提升线程在队列上发出请求，目标线程需要一个循环，读取队列中的请求并执行它们。也许这听起来很熟悉，是的，这是程序的UI线程的工作方式。

I am having trouble finding a c# example that shows how to raise a cross-thread event in the following condition:

Let's say I have 1 Event and 3 Threads:

Event DoStuff

Thread A - WinForm

Thread B - Thread Spawned from Thread A to do some processing. Has Function Foo() which is subscribed to DoStuff

Thread C - Thread Spawned from Thread B to do some subprocessing and Raises event DoStuff

Now How do I ensure that The event Raised in Thread C is processed inside of Thread B instead of C or A.

All of the samples I run accross hint towards Form/Control.Invloke, or somthing of that sort, where I really actually want to have whatever Thread actually subscribed to the event execute inside of it's repsective thread, not just the Main Form Thread.

解决方案

Marshaling a call from one thread to specific other thread is highly untrivial. It is not possible to arbitrarily interrupt the thread and make it execute some code. That causes horrible re-entrancy problems. Trying to protect against that with, say, a semaphore is guaranteed to cause deadlock.

The target thread has to cooperate, it must be 'idle' and not actively mutating the state of the program. A common mechanism for that is a thread-safe queue. The event raising thread puts a request on the queue, the target thread needs a loop that reads the requests off the queue and executes them. Maybe this sounds familiar, yes, that's the way the UI thread of a program works.

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