How to pass Button.Click into a function?

Question

I have a function that adds eventhandlers to control events. Right now I have several overloads that add events to different types of controls:

Public Sub AddEventHandler(Button, ButtonEvent) 'adds event handling for Button.Click
public Sub AddEventHandler(LinkButton, ButtonEvent)'adds event handling for LinkButton.Click

The problem is I want to write a function that is more robust like:

Public sub AddEventHandler(Control, EventToHandle, ControlEvent)

where

EventToHandle is the parameter representing Button.Click or whatever event that Button has associated with it.

Any suggestions guys? Thanks!

Answer 1

The right way is probably done using reflection. A simpler way, however, would be to do something like this.

(Code is in C#, but conversion is pretty trivial.)

private void AddEventHandler(Control c, Event e){
    if(c is LinkButton){
        ((LinkButton)c).Click += e;
    }
    else if(c is Button){
         ((Button)c).Click += e;
    }
    /* etc */
}

If you sometimes want to do an event that isn't "Click" you could pass a string representing the event name as a third argument and wrap it thusly:

if(what_event == "Click"){
    if(c is LinkButton){
        ((LinkButton)c).Click += e;
    }
    /* etc */
}
else if(what_event == "SelectedIndexChanged"){
    if(c is DropDownList){
        ((DropDownList)c).SelectedIndexChanged += e;
    }
    /* etc */
}

Sucks but it works and might be more compact than what you have now.

Answer 2

You still can do something like this:

private void Subscribe<TControl>(TControl control, Action<TControl, EventHandler> subscriber, EventHandler handler)
{
    subscriber.Invoke(control, handler);
}

And using:

   Subscribe(this, (control, handler) => control.Load += handler, LoadHandler);

But I don't think it is better then actually subscribing to the event.