Question

I am using events as a publisher/subscriber pattern in c#. However I dont know at design time how many publishers my program will be using. I would like to dynamically add events to either a class directly, or more plausibly to a collection/dictionary containing the events.

Are either of these scenarios possible using C#?

Answer 1

Create a mediator that your publishers publish to and that your subscribers subscribe to. For example:

public class Mediator
{
    public static readonly Mediator Current = new Mediator();
    public event EventHandler<EventArgs> EventRaised;
    public void RaiseEvent(object sender, EventArgs eventArgs)
    {
        if (EventRaised!=null) 
            EventRaised(sender, eventArgs);
    }
}
public class PublisherEventArgs : EventArgs
{
    public string SomeData { get; set; }
}
public class Publisher
{
    public void Publish(string data)
    {
        Mediator.Current.RaiseEvent(this, new PublisherEventArgs() { SomeData = data} );
    }
}
public class Subscriber
{
    public Subscriber()
    {
        Mediator.Current.EventRaised += HandlePublishedEvent;
    }

    private void HandlePublishedEvent(object sender, EventArgs e)
    {
        if(e is PublisherEventArgs)
        {
            string data = ((PublisherEventArgs)e).SomeData;
            // todo: do something here
        }
    }
}

Make sure you implement IDisposable on your subscriber (its not in my example) so that it unsubscribes from the Mediator during dispose.