Question

I have the following code which is working but it is very dirty. Actually the code is just fine except the part I added: a pause and a stop button. I’m new to c# so any help would be apreciated.

    private void pause_button_Click(object sender, EventArgs e)
    {
        start = false; pause = true; stop = false;
        guiUpdate();
        PauseEvent.Reset();
    }

    private void stop_button_Click(object sender, EventArgs e)
    {
        if (pause == true)
        {
            PauseEvent.Set();
            pause = false;
            this.start_button.Click -= new System.EventHandler(this.resume_button_Click);
        }
        start = false; stop = true;
    }

    private int activeThreads = 0;
    private Thread thread;
    private void DoWork(object sender)
    {
        string line = null;
        ereader = new StreamReader(MY_LIST);
        do
        {
            lock (ereader)
            {
                PauseEvent.WaitOne();
                line = ereader.ReadLine();
            }

            //
            //other commands for processing & building the argument
            //

            lock (signal)
            {
                ++activeThreads;
            }

            thread = new Thread(new ParameterizedThreadStart(
                o =>
                {
                    processit((object)o);
                    lock (signal)
                    {
                        --activeThreads;
                        Monitor.Pulse(signal);
                    }
                }));
            thread.Start(argument);

            lock (signal)
            {
                while (activeThreads > maxthreads)
                    Monitor.Wait(signal);
            }

            lock (signal)
            {
                if (!start)
                {
                    showwaiting(true);//shows an animated gif with a "please wait" msg
                    while (activeThreads > 0)
                        Monitor.Wait(signal);
                    showwaiting(false);
                    if (stop == true)
                    {
                        this._BackgroundWorker.CancelAsync();
                        break;
                    }
                }
            }
        }
        while (ereader.Peek() != -1);
        showwaiting(true);
        lock (signal)
        {
            while (activeThreads > 0)
                Monitor.Wait(signal);
        }
        showwaiting(false);
    }


    private void _BackgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        start = false; stop = true;
        guiUpdate();
    }

what exactly can I do to avoid those duplicate commands inside and outside the loop ?

Answer 1

Mentioned in the question comments are suggestions about code practice changes.

• Do not use == true or == false when checking a boolean variable in a condition. (Jeff)
• Use an enumerate to represent the state instead of multiple boolean variables.

I would also add:

• Use proper C# naming conventions. For your methods if there are multiple words, capitalize all words. (e.g. instead of showwaiting use ShowWaiting).

For your small loops, you don’t really need to optimize them out though there is more than a simple loop. So you could refactor them to a separate method along with all the code that is the same:

private void ShowAndWait()
{
    showwaiting(true);
    lock (signal)
    {
        while (activeThreads > 0)
            Monitor.Wait(signal);
    }
    showwaiting(false);
}

Note that it is fine for the same thread to lock on a monitor that it previously acquired. This is a fast operation since the thread already owns the lock. You can then call this method from both places.