从子方法中终止父方法

Question

I create a plugin for an application. When a user presses a stop command in the parent application, a global variable to which my plugin has access to is set to true. For a simple method I create, I test this variable and exit:

public class Status
{
    public static bool CheckTermFlag()
    {
        if (VoiceAttackPlugin._stopVariableToMonitor)
        {
            VoiceAttackPlugin._stopVariableToMonitor = false;
            return true;
        }
        return false;
    }
}

And I place this 'CheckTermFlag' in my code:

class ForTesting
{
    public static void SendStopAllTest()
    {
        for (int i = 0; i <= 20; i++)
        {
            if (Status.CheckTermFlag())
            {
                return;
            }
            Thread.Sleep(500);
            vaProxy.WriteToLog(i.ToString(), "Green");
        }
    }

The problem is that I may have several methods and each calling another one. I can't place a question for "Status.CheckTermFlag()" in every step of my program and propagate it upwards.

So how can i 'listen' for this variable from anywhere in my program and terminate/return if required?

Answer 1

Why not use a CancellationToken for this? You can stop any method by any method that way. If a method have access to CTS it can just call Cancel and all methods that have CancellationToken s can then finish whatever they are doing and exit.

In multithreading environment a SemaphoreSlim can be used as an awaitable reset event as a mean of synchronizing threads.

I wouldn't use Thread.Abort() , it's good for the threads you have no control over. But if it's all your code and you control it - it's always better just to signal between threads and ask them nicely to terminate, that leads to less undefined states and behaviors later.

BTW, just make either the CancellationTokenSource accessible to methods that should stop the calling method, or made an accessible method that calls Cancel() on CTS . I used that approach a lot in a high-load.network gateway and a desktop application that downloaded a large number of files parallelly. The cost of it is negligible. Don't be afraid of disposables, used correctly they save more time than it takes to handle them.

Answer 2

In a multi-threaded scenario the way to go is the Thread.Abort() method. It throws the ThreadAbortException in the target thread, causing it to terminate.

If you, for whatever reason, need a custom solution, do it likewise. Throw an exception, and handle it at the top-most method where it makes sense. Like this:

public class TerminateProcessingExeption : Exception { … }

…

public static bool CheckTermFlag()
{
    if (VoiceAttackPlugin._stopVariableToMonitor)
    {
        VoiceAttackPlugin._stopVariableToMonitor = false;
        throw new TerminateProcessingExeption();
    }
}

In addition, instead of a bool flag, consider using an AutoResetEvent . Look into the example in the documentation for more information. A simple variable won't shield you from the adverse effects of concurrent memory access in multi-processor setups.