[Mono-list] Little question ...

[Jaroslaw Kowalski]

I believe that events are there to solve the problem overwriting the
devegate instead of appending a new handler to it.

Events only support add/remove (+=, -=), there's no support for assignment.

All you can do is:

myObject.RightListItemChanged += new EventHandler (myObject_ItemChanged);
myObject.RightListItemChanged -= new EventHandler (myObject_ItemChanged);

With delegates you would be able to:

myObject.RightListItemChanged = new EventHandler (myObject_ItemChanged);

which would overwrite all handlers in the delegate chain.

Jarek

----- Original Message ----- 
From: "Nick Berardi" <nberardi@zigamorph.com>
To: <mono-list@lists.ximian.com>
Sent: Thursday, February 19, 2004 9:13 PM
Subject: RE: [Mono-list] Little question ...


> Sergio,
>
> Events are more like delegate properties.  Such is you can do the
following.
> This is good if you want to encapsulate a child objects event.  Such as
how
> I am doing it below.  When somebody calls the following:
>
> myObject.RightListItemChanged += new EventHandler (myObject_ItemChanged);
>
> this is what happens underneath in the code.  It sets the child objects
> SelectedItemChange to the method that I selected above.  Even though it is
> twice removed.  In addition it enabled AutoPostBack.
>
> public event EventHandler RightListItemChanged {
> add
> {
> deniedListBox.SelectedIndexChanged += value;
> deniedListBox.AutoPostBack = true;
> }
> remove
> {
> deniedListBox.SelectedIndexChanged -= value;
> deniedListBox.AutoPostBack = false;
> }
> }
>
> -----Original Message-----
> From: mono-list-admin@lists.ximian.com
> [mailto:mono-list-admin@lists.ximian.com] On Behalf Of Sergio Blanco
> Cuaresma
> Sent: Thursday, February 19, 2004 2:56 PM
> To: mono-list@lists.ximian.com
> Subject: Re: [Mono-list] Little question ...
>
> El sáb, 07-02-2004 a las 17:21, Miguel de Icaza escribió:
> > Hey,
> >
> > > Only one little question: What are the main differences between using
> > > "event" keyword or not when creating delegates?
> > >
> > > Example:
> > >
> > > delegate void ProbeDelegate  (string msg);
> > >
> > > ProbeDelegate d1;
> > > event ProbeDelegate d2;
> >
> > events can notify more than one function, a delegate only points to a
> > single method.
> >
> > So you can have multiple "listeners".
>
> But, only using delegates you can do:
>
>   DelegadoOperacion multiD;
>   multiD = new DelegadoOperacion(s.suma);
>   multiD += new DelegadoOperacion(s.resta);
>
> And then call multiD which will call more than one method. So what is
> the real difference with events ??
>
> Sergio.
>
> -- 
>
> [aka Marble]
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