Trying to understand the event aggregator pattern

Question

I am trying to implement the event aggregator pattern in a simple way to learn it step by step. But i didn't find any book or nice video tutorial talking about it's implementation.
I just found some good articles such as this http://weblogs.asp.net/rashid/archive/2009/03/05/use-event-aggregator-to-make-your-application-more-extensible.aspx and http://martinfowler.com/eaaDev/EventAggregator.html the first article is too big to let me understand the pattern and the second one is not completed :).
By the way i created my classes:

public class Member
{
    public int ID { get; set; }

    public string UserName { get; set; }
}

public class MemberService
{
    public void CommentSubmited()
    {
        // increase member score and do some other logic.
    }
}

public class Comment
{
    public int ID { get; set; }

    public string CommentBody { get; set; }

    public Member ByMember { get; set; }
}

public class CommentService
{
    public void SubmitNewComment(Member member, string commentBody, EventAggregator eventAggregator)
    {
        Comment comment = new Comment();
        comment.ByMember = member;
        comment.CommentBody = commentBody;

        db.SaveComment(comment); // save comment to the db

        //eventAggregator.GetEvent<CommentSubmited>.Fire();
    }
}

public class EventAggregator
{
    public void RegisterEvent()
    {

    }

    public void RemoveEvent()
    {

    }
}

And what i want is to create a generic way so that when ever a new comment created the CommentSubmited() method to Fire.
I want it generic because there will be more services later such as RateService, QuestionService, .... and each one will have a XXXSubmited() method in the MemberService class.

Hope you understood what i want to learn, ask me if you want me to make things more clear.

Note i checked the Generic Delegates topic and thought it may help me in this issue, but couldn't make it as i wanted.

Garda

Answer 1

Check out this post on a simple event aggregator using Rx: Event Aggregator with Reactive Extensions

Berkow

the article is nice, but i can't imagine how the ISubject and Subject will look like, he didn't write them in his example. – Garda

In case anyone stumbles in here, Amr posted on finding ISubject and someone pointed out that they are in Reactive Extensions: #3439919 – Containerize

Answer 2

Karl Shifflett (Microsoft patterns and practices team) made a video where he walks through the Event Aggregator pattern and explains how he used it in his Stuff WPF/MVVM application. His blog entry has more about his project and the source code is available for download as well. I found his example application and videos to be really helpful as I was learning.

Registration