In the previous article, I’ve proposed a simple way to create a multi-thread queue for a producers-consumes process. As I said, the library was developed for .NET 3.5.
.NET 4.0 has a new set of classes that realized this kind of function, in details the
BlockingCollection realized a queue.
.NET 4.0 provides a new spacename System.Collections.Concurrent that contains the new classes for multi-thread collections. The use of these classes is not complicated, but I’ve written a simple library – like the previous one – that makes the job simpler. Particularly, this library provides a simple way for creating a pool of dequeuer threads.
Using the Code
The library can be used inside every project. This first draft is composed of 4 classes and one interface as described in the following table:
|It’s the interface for a multi-thread collection. It’s necessary to have a non-type interface.
|It’s the generic class that implements the above interface.
abstract class for a dequeuer thread. The
OnNewElement method should be implemented in inherited classes.
|It’s the basic class with the params for instantiating the dequeuer.
|It’s the dequeuer pool.
To create the queue, you have to instance a type class of the
MultiThreadBlockingQueue generic class.
MultiThreadBlockingQueueLib.MultiThreadBlockingQueue<double> queue =
Reading the values inserted in the queue is very simple. You have to create a new class inherited from
MultiThreadDequeuer and define the method
OnNewElement for this new class. This method is called every time a new element is available on the queue.
class ThreadDequeuer : MultiThreadBlockingQueueLib.MultiThreadDequeuer
public ThreadDequeuer(MultiThreadBlockingQueueLib.MultiThreadDequeuerParams p)
protected override void OnNewElement(object element)
To start the reader(s), you have to instance your dequeuer class(es) and then call the method
You can also quickly create a pool of dequeuers. You just have to instance a
MultiThreadDequeuerPool class and then initialize the pool by the
Init method to define the number of threads and the class to use as a dequeuer. Then start and stop all the threads by the pool methods
Shutdown. Also, you can dynamically add a new thread by the method
MultiThreadBlockingQueueLib.MultiThreadDequeuerPool dequeuerPool =
Points of Interest
BlockingCollection provides the method
Take to wait for a new item in the collection and take it. If you want to stop this method, you have to use a
Therefore, the dequeuer has to instance a
System.Threading.CancellationTokenSource class in order to pass a
CancellationToken to the
Take method. When you want to stop, call the
Cancel method of the
CancellationTokenSource. See the
MultiThreadDequeuer to check how it works.