How can a child thread notify a parent thread of its status/progress?

Question

I have a service responsible for many tasks, one of which is to launch jobs (one at a time) on a separate thread (threadJob child), these jobs can take a fair amount of time and

have various phases to them which I need to report back.

Ever so often a calling application requests the status from the service (GetStatus), this means that somehow the service needs to know at what point the job (child thread) is

at, my hope was that at some milestones the child thread could somehow inform (SetStatus) the parent thread (service) of its status and the service could return that information

to the calling application.

For example - I was looking to do something like this:

class Service
{
private Thread threadJob;
private int JOB_STATUS;

public Service()
    {
    JOB_STATUS = "IDLE";
    }

public void RunTask()
    {
    threadJob = new Thread(new ThreadStart(PerformWork));
    threadJob.IsBackground = true;
    threadJob.Start();
    }

public void PerformWork()
    {
    SetStatus("STARTING");
    // do some work //
    SetStatus("PHASE I");
    // do some work //
    SetStatus("PHASE II");
    // do some work //
    SetStatus("PHASE III");
    // do some work //
    SetStatus("FINISHED");
    }

private void SetStatus(int status)
    {
    JOB_STATUS = status;
    }

public string GetStatus()
    {
    return JOB_STATUS;
    }

};

So, when a job needs to be performed RunTask() is called and this launches the thread (threadJob). This will run and perform some steps (using SetStatus to set the new status at

various points) and finally finish. Now, there is also function GetStatus() which should return the STATUS whenever requested (from a calling application using IPC) - this status

should reflect the current status of the job running by threadJob.

So, my problem is simple enough... How can threadJob (or more specifically PerformWork()) return to Service the change in status in a thread-safe manner (I assume my example above of SetStatus/GetStatus is

unsafe)? Do I need to use events? I assume I cannot simply change JOB_STATUS directly ... Should I use a LOCK (if so on what?)...

Answer 1

You may have already looked into this, but the BackgroundWorker class gives you a nice interface for running tasks on background threads, and provides events to hook into for notifications that progress has changed.