BlockingCollection multiple consumer

Question

I have the following code with one producer thread and multiple consumer threads. Do you know if multiple consumers are thread safe. For example is there any chance that thread 1 is consuming and while do that thread 2 consume in parallel and change the value of the item that is used in thread 1?

namespace BlockingColl
{
public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    private void button1_Click(object sender, EventArgs e)
    {
        try
        {
            for (int i = 0; i < 3; i++)
            {

                ThreadPool.QueueUserWorkItem((x) =>
                   {
                       foreach (var item in bc.GetConsumingEnumerable())
                       {
                           Console.WriteLine(Thread.CurrentThread.ManagedThreadId + " - " + item + " - " + DateTime.Now.ToString("MM/dd/yyyy hh:mm:ss.fff tt"));
                       }
                   });
            }
        }
        catch (Exception)
        {

            throw;
        }
    }

    private void button2_Click(object sender, EventArgs e)
    {
        for (int i = 0; i < 3; i++)
        {

            ThreadPool.QueueUserWorkItem((x) =>
               {
                   Cache.Consume();
               });
        }


        for (int i = 0; i < 50000; i++)
        {
            Cache.bc.TryAdd(new Client() { ClientId = i, ClientName = "Name" + i });
        }
    }
}

static class Cache
{
    public static BlockingCollection<Client> bc = new BlockingCollection<Client>();


    public static void Consume()
    {
        foreach (var item in bc.GetConsumingEnumerable())
        {
            Console.WriteLine(Thread.CurrentThread.ManagedThreadId + " - " + item + " - " + DateTime.Now.ToString("MM/dd/yyyy hh:mm:ss.fff tt"));
        }
    }
}

public class Client
{
    public int ClientId { get; set; }
    public string ClientName { get; set; }
}
}

Thanks in advance

fsimonazzi fsimonazzi · Accepted Answer · 2012-11-02T14:11:46

Once you've consumed an element it is removed from the collection, so no other thread will be able to access it (at least through the collection).

That Cache looks more like a buffer to me. What does it add on top of the blocking collection anyway? It's weird that the cache would be able to consume its own elements.

BlockingCollection multiple consumer

2 Answers