Question

I’m trying to implement simple Event Bus

I started like this:

public class RegistrationData
{
    public object RegisteredObject { get; set; }
    public Type eventType { get; set; }
    public EventHandler MethodToInvoke;
}
public class EventBus
{
    private static EventBus instance;
    private static readonly object lockObject = new object();
    private static List<RegistrationData> registrationList;

    private EventBus()
    {
    }

    public static EventBus Instance
    {
        get
        {
            lock (lockObject)
            {
                registrationList = new List<RegistrationData>();
                return instance ?? new EventBus();
            }
        }
    }

    public void Subscribe(RegistrationData registrationData)
    {
        if(!registrationList.Contains(registrationData)) registrationList.Add(registrationData);
    }

    public void Unsubscribe(object objectToUnregister, Type eventType)
    {
        foreach(RegistrationData data in registrationList)
            if (data.RegisteredObject == objectToUnregister && data.eventType == eventType) registrationList.Remove(data);
    }

    public void UnregisterAllMessages(object objectToUnregister)
    {
        foreach(RegistrationData data in registrationList)
            if(data.RegisteredObject == objectToUnregister) registrationList.Remove(data);
    }

    public void PublishEvent(object sender, EventArgs eventArgs)
    {
        foreach (RegistrationData data in registrationList)
            if (EventArgs is typeof(data.Type)) data.MethodToInvoke(sender, eventArgs);
    }
}

But I have problem in PublishEvent method. I’m unable to determine type of event argument.
And I’m suspicious that all this is pretty wrong.

Can someone point out what I do wrong, how should I implement this?
Or how event bus is generally implemented, or some framework which I can use instead of implementing my own and spending time on that.

Answer 1

Um, not really sure how your Eventbus should behave. Short of knowing where you are heading it can be useful to look at how other people implemented the problem.

• There is a down-to-earth event aggregator in the caliburn.micro project
• I like to use MemBus when I need an event aggregator, partly because I wrote it myself, partly because it covers all my needs in that respect. It is more involved than caliburn’s one, but then it has more features