Question

public class Human
{
    public void Run(){}
    public void Jump(){}
    public void Eat(){}

    //Generalized approach
    public EventHandler<HumanActivityProgressChanged> ActivityProgressChanged;
    public EventHandler<HumanActivityCompleted> ActivityCompleted;

    //Per-method approach
    public EventHandler<HumanActivityProgressChanged> Running;
    public EventHandler<HumanActivityCompleted> Ran;

    public EventHandler<HumanActivityProgressChanged> Jumping;
    public EventHandler<HumanActivityCompleted> Jumped;

    public EventHandler<HumanActivityProgressChanged> Eating;
    public EventHandler<HumanActivityCompleted> Ate;
}

I have different methods that implements Event-based Async pattern. These methods trigger a ProgressChanged eventargs and a Completed eventargs. They all trigger the same eventargs (As shown in the code above).

Does it make sense to provide an event per each async method? Or just provide a generalized event for all async methods? Is there such a thing as too much events?

Answer 1

Both are valid. It really depends on what your intention is.

Will you expect a listener to want to listen to all events and repond in similar ways? Go fot the generalized event.

If you are expecting a load of disparate listeners each interested in different aspects, performing wildly different tasks on these events, go for the second.

The idea behind api design is not to impose a certain way of usage on the clients (Rails users may disagree), but you will give strong hints in the way you design it..