Question

I have a .NET 4.0 ASP.NET project which requires some threading work I’ve never really messed with before and I’ve been looking at this for days and I’m still clueless =/

Basically I want something like when you take a ticket at the deli and wait your turn before they get back to you. I’ll try and relate this and see if it makes any sense…

function starts —> gets to section where it needs to “take a ticket” (I assume queue some type of item in a blockingcollection) and waits until other “tickets” (a.k.a other instances of the same function) are completed before it gives the function the OK to resume (blocking collection gets to the item in the queue) —> finish function.

I don’t need/want to do any work in the queue, I just want the function to statically wait it’s turn among other instances of the function. Does that make sense? Is that possible?

Please provide code if possible as I’ve seen tons of examples but none of them make sense/don’t do what I want.

Answer 1

Alright so after researching document after document and playing with numerous rewrites of code I finally figured out I wasn’t using the AutoResetEvent right and how to use a blocking collection on a dedicated thread. So here was the final solution using an AutoResetEvent with a BlockingCollection. This solution below might not show the same results 100% of the time (just because I believe it has to do with thread timing of when something was entered into the blocking collection) but the end result is that it does exactly what I want.

class Program
{
    static void Main(string[] args)
    {
        TaskProcessor tp = new TaskProcessor();

        Thread t1 = new Thread(new ParameterizedThreadStart(tp.SubmitRequest));
        t1.Start(1);

        Thread t2 = new Thread(new ParameterizedThreadStart(tp.SubmitRequest));
        t2.Start(2);

        Thread t3 = new Thread(new ParameterizedThreadStart(tp.SubmitRequest));
        t3.Start(3);         
    }
}

class TaskProcessor
{
    private AutoResetEvent _Ticket;

    public TaskProcessor()
    {
        _Continue = new AutoResetEvent(false);
    }

    public void SubmitRequest(object i)
    {
        TicketingQueue dt = new TicketingQueue();

        Console.WriteLine("Grab ticket for customer {0}", (int)i);

        dt.GrabTicket(_Ticket);

        _Continue.WaitOne();

        Console.WriteLine("Customer {0}'s turn", (int)i);
    }
}

public class TicketingQueue
{
    private static BlockingCollection<AutoResetEvent> tickets = new BlockingCollection<AutoResetEvent>();

    static TicketingQueue()
    {
        var thread = new Thread(
          () =>
          {
              while (true)
              {                      
                  AutoResetEvent e = tickets.Take();
                  e.Set();
                  Thread.Sleep(1000);
              }
          });
        thread.Start();
    }

    public void GrabTicket(AutoResetEvent e)
    {
        tickets.Add(e);
    }
}