It is possible to pass data to EventArgs without creating derived class?

Question

I am a bit confused. I know I can create class derived from EventArgs in order to have custom event data. But can I employ the base class EventArgs somehow? Like the mouse button click, in the subscriber method, there is always "EventArgs e" parameter. Can I create somehow the method that will pass data this way, I mean they will be passed in the base Eventargs?

Answer 1

You can use the EventArgs class through the Generic Types approach. In this sample, i will use the Rect class with as return type:

public EventHandler<Rect> SizeRectChanged;

Raising the event:

if(SizeRectChanged != null){
   Rect r = new Rect(0,0,0,0);
   SizeRectChanged(this,r);
}

Listening the event:

anyElement.SizeRectChanged += OnSizeRectChanged;

public void OnSizeRectChanged(object sender, Rect e){
    //TODO abything using the Rect class
    e.Left = e.Top = e.Width = e.Height = 50;
}

So, don't need to create new events classes or delegates, simply create a EventHandler passing the specific type T.

Answer 2

Nope. The EventArgs base class is just a way to allow for some standard event delegate types. Ultimately, to pass data to a handler, you'll need to subclass EventArgs. You could use the sender arg instead, but that should really be the object that fired the event.