Question

So first here is some pseudo code of what I want to improve.

        public List<ProcessData> Processes;
        System.Threading.Thread ProcessThread;
        void ProcessLoop()
        {
            while (true)
            {
                for (int i = 0; i < Processes.Count; i++)
                {
                    if (HasPriority(Processes[i]))
                    {
                        Process(Processes[i]);
                    }
                }
                System.Threading.Thread.Sleep(1000);
            }

        }
        void AddProcessData(ProcessData pd)
        {
            Processes.Add(pd);
            if (Suspended(ProcessThread))
                Resume(ProcessThread);
        }
        void Startup()
        {
            ProcessThread = new System.Threading.Thread(ProcessLoop);
            ProcessThread.Start();
        }

So what I want to do is replace the ‘Sleep’ with code that will suspend the thread or have it wait until something is added to the list and then resume it. I also need it to be thread safe of course.

Answer 1

What you want is an event.

EDIT: to make it thread-safe.

    public List<ProcessData> Processes;
    System.Threading.Thread ProcessThread;
    System.Threading.AutoResetEvent ProcessesChangedEvent = new System.Threading.AutoResetEvent(false);
    void ProcessLoop()
    {
        while (true)
        {
            // You might want to copy out the entire list as an array instead 
            // if HasPriority or Process take a long time.
            lock (Processes)
            {
                for (int i = 0; i < Processes.Count; i++)
                {
                    if (HasPriority(Processes[i]))
                    {
                        Process(Processes[i]);
                    }
                }
            }
            ProcessesChangedEvent.WaitOne(...); // timeout?
        }

    }
    void AddProcessData(ProcessData pd)
    {
        lock (Processes)
            Processes.Add(pd);
        ProcessesChangedEvent.Set(); // you can also use Monitor.PulseAll/Wait
    }
    void Startup()
    {
        ProcessThread = new System.Threading.Thread(ProcessLoop);
        ProcessThread.Start();
    }