Question

I need to call a 3rd party code that optionally starts a new thread, performs some processing, and then calls a different method on my object. What I need is wait for the 3rd party processing to be finished, then return from the original method. In other words, I have a class like this (C#):

class MyClass: IThirdPartyInterface {
    void MyMethod() {
        //some preprocessing
        //call a 3rd party static method
        ThirdParty.DoSomething(this);
     }
    void FinishedProcessing() {
        //some postprocessing
        //???
    }
}

I want to modify MyMethod so that it return only after the thread that started in DoSomething has finished its execution and called the FinishedProcessing method. Since the thread is started by the third party code, I don’t have access to it, so I cannot use Thread.Join here. So, what do I do instead?

Answer 1

You need to use an System.Threading.AutoResetEvent, it would be like this:

class MyClass: IThirdPartyInterface {
    AutoResetEvent _event = new AutoResetEvent(false);
    void MyMethod() {
        ThirdParty.DoSomething(this);
        _event.WaitOne();
    }
    void FinishedProcessing() {
        _event.Set();
    }
}

If the thread continues running after your FinishedProcessing method is called by the 3rdparty class, it would be a little diferent:

class MyClass: IThirdPartyInterface {
    AutoResetEvent _event = new AutoResetEvent(false);
    Thread _thread;
    void MyMethod() {
        ThirdParty.DoSomething(this);
        _event.WaitOne();
        _thread.Join();
    }
    void FinishedProcessing() {
        _thread = Thread.CurrentThread;
        _event.Set();
    }
}