Re: Consuming your own events.

I'm interested in your RaiseXXX and HandleXXX pattern of methods.
Can you post an example of how you implement it?

I have used for quite some time the OnXXX pattern myself.
I have strictly adhered to the the convention that the only code that goes
in the method is this:

protected virtual void OnXXXX(EventArgs e){
    if (MyEvent != null)
        MyEvent(this, e);
}


On Jan 30, 2008 7:24 AM, Sebastien Lambla <[email protected]> wrote:

> What happens when you use two libraries, one using OnXxx as event handling
> virtual methods, one using it as event raising virtual methods? When you
> mix
> the two in the same project it becomes very confusing, documentation or
> not.
>
> I can't think of any generic test that could differentiate between
> forgetting to call the base OnXxx method and the one that does it on
> purpose.
>
> Compare that to Cancel = true, non virtual RaiseXxx and protected virtual
> HandleXxx... Compiler-checked and testable.
>
>
> --
> SerialSeb
> http://serialseb.blogspot.com
>
>
> > -----Original Message-----
> > From: Discussion of development on the .NET platform using any managed
>  > language [mailto:[email protected]] On Behalf Of Frans
> > Bouma
> > Sent: 30 January 2008 13:06
> > To: [email protected]
> > Subject: Re: [DOTNET-CLR] Consuming your own events.
> >
> > > Most developers have to use multiple frameworks in their day-to-day
> > jobs.
> > >
> > > The fact that multiple frameworks use the OnXxx naming convention
> > > differently introduces consistency issues that directly impact the
> > > robustness of your code, especially when you build frameworks for
> > others.
> >
> >         Sure, but that's unavoidable: there are always guidelines which
> > are
> > contradicting, so which one to follow? earlier today I showed that the
> > Webforms' DataSourceControl uses different methods than winforms for
> > the same
> > thing, which one to follow?
> >
> >         The best and only thing you can do is:
> > 1) be consistent inside your own framework
> > 2) document things properly.
> >
> > > When something smells badly, you can try and take the point of view
> > that one
> > > of the implementation choices is the right one, apply it, and expect
> > > developers to understand and accept your view of the pattern, or you
> > can
> > > avoid it like the plague and define better semantics to solve the
> > problem
> > > once and for all.
> >
> >         Then still you run the risk of it being
> > misunderstood/misinterpreted.
> > The one true thing you need is proper documentation: if it's properly
> > described what to do and what the methods stand for, there's no
> > confusion and
> > no problem.
> >
> >         Sure if people refuse to read documentation or are too stupid
> > to write
> > the documentation, then things are out of control. Darwin....
> >
> >                 FB
> > >
> > > --
> > > SerialSeb
> > > http://serialseb.blogspot.com
> > >
> > >
> > > > -----Original Message-----
> > > > From: Discussion of development on the .NET platform using any
> > managed
> > > > language [mailto:[email protected]] On Behalf Of
> > Sébastien
> > > > Lorion
> > > > Sent: 30 January 2008 12:41
> > > > To: [email protected]
> > > > Subject: Re: [DOTNET-CLR] Consuming your own events.
> > > >
> > > > Well, I understand your scenario better now, but ... this is (up to
> > > > now) specific to WPF and it is not the first time that the one
> > making
> > > > guidelines is breaking them .... *cough* binding *cough*.
> > > >
> > > > Why would this apply to, say, ObservableCollection<T> ?
> > > >
> > > > Sébastien
> > > >
> > > > On 1/30/08, Sebastien Lambla <[email protected]> wrote:
> > > > > I'm talking about using attached events that your type is not an
> > > > owner of.
> > > > > For example
> > > > >
> > > > > public event MouseButtonEventHandler MouseDown
> > > > > {
> > > > >     add
> > > > >     {
> > > > >         this.AddHandler(Mouse.MouseDownEvent, value, false);
> > > > >     }
> > > > >     remove
> > > > >     {
> > > > >         this.RemoveHandler(Mouse.MouseDownEvent, value);
> > > > >     }
> > > > > }
> > > > >
> > > > >
> > > > > Now let's see what the OnMouseDown method is.
> > > > >
> > > > > protected virtual void OnMouseDown(MouseButtonEventArgs e)
> > > > > {
> > > > > }
> > > > >
> > > > > Sparing you with the nasty details:
> > > > > EventManager.RegisterClassHandler(typeof(UIElement),
> > > > Mouse.MouseDownEvent,
> > > > > new MouseButtonEventHandler(UIElement.OnMouseDownThunk), true);
> > > > >
> > > > >
> > > > > So the next generation UI framework uses OnXxx for event handling
> > > > (not
> > > > > raising!). Raising itself uses the RaiseEvent method.
> > > > >
> > > > > This conflicts with the guidelines that have been discussed,
> > conflict
> > > > less
> > > > > with the ones i've just explained. Because of that, I advise
> > against
> > > > using
> > > > > the On notation, to prevent the confusion introduced by different
> > > > > frameworks...
> > > > >
> > > > > --
> > > > > SerialSeb
> > > > > http://serialseb.blogspot.com
> > > > >
> > > > >
> > > > > > -----Original Message-----
> > > > > > From: Discussion of development on the .NET platform using any
> > > > managed
> > > > > > language [mailto:[email protected]] On Behalf Of
> > > > Sébastien
> > > > > > Lorion
> > > > > > Sent: 30 January 2008 11:45
> > > > > > To: [email protected]
> > > > > > Subject: Re: [DOTNET-CLR] Consuming your own events.
> > > > > >
> > > > > > On 1/30/08, Sebastien Lambla <[email protected]> wrote:
> > > > > > >
> > > > > > > When you start, like in WPF, using different property stores
> > for
> > > > your
> > > > > > > events, the problem becomes even worse (and it's that problem
> > > > that
> > > > > > has
> > > > > > > triggered my move to this new pattern).
> > > > > >
> > > > > >
> > > > > > Could you elaborate on this bit, I am not sure I follow you. I
> > > > think
> > > > > > you mean to use a hashtable to associate events to their
> > delegate
> > > > > > instead of default
> > > > > > storage (ie one field by event) ? If so, how is it affected by
> > the
> > > > > > OnXXX pattern ?
> > > > > >
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> > > >
> > > >
> > > > --
> > > > Sébastien
> > > > www.sebastienlorion.com
> > > >
> > > > ===================================
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