Yeah that is true and I don't think anybody is debating that event is very limited in what it can do. But I think he was more asking why have events.
The "no support for assignment" is something that I forgot to include in my last e-mail. Here is the text from the actual language specification. " Since += and -= are the only operations that are permitted on an event outside the type that declares the event, external code can add and remove handlers for an event, but cannot in any other way obtain or modify the underlying list of event handlers. In an operation of the form x += y or x -= y, when x is an event and the reference takes place outside the type that contains the declaration of x, the result of the operation has type void (as opposed to having the type of x, with the value of x after the assignment). This rule prohibits external code from indirectly examining the underlying delegate of an event. " In addition there is a special attribute modifier for events, like the following. [event: MyEventAttribute] public event EventHandler MyEvent; delegates have one but it is defined the same that a class is. (i.e. [type: MyClassAttribute]) Hope this helped out a little. -----Original Message----- From: Jaroslaw Kowalski [mailto:[EMAIL PROTECTED] Sent: Thursday, February 19, 2004 3:46 PM To: Nick Berardi; [EMAIL PROTECTED] Subject: Re: [Mono-list] Little question ... 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" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> 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: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Sergio Blanco > Cuaresma > Sent: Thursday, February 19, 2004 2:56 PM > To: [EMAIL PROTECTED] > Subject: Re: [Mono-list] Little question ... > > El s�b, 07-02-2004 a las 17:21, Miguel de Icaza escribi�: > > 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] > Web Personal <> http://www.marblestation.com > Registered LiNUX user #140941 <> http://counter.li.org/ > Socio #3274 de HispaLinux <> http://www.hispalinux.es > Miembro de GPL URV <> http://www.gplurv.org > GnuPG key: 0x0ED2CF9D <> hkp://pgp.escomposlinux.org > > _______________________________________________ > Mono-list maillist - [EMAIL PROTECTED] > http://lists.ximian.com/mailman/listinfo/mono-list > _______________________________________________ Mono-list maillist - [EMAIL PROTECTED] http://lists.ximian.com/mailman/listinfo/mono-list
