[Gtk-sharp-list] Attaching method to events without explicit EventHandler instanciation

Charles-Henri d'Adhémar cdadhemar at gmail.com
Sat Feb 23 05:06:00 EST 2008

Thank you very much Chris for your very clear explanations (are you a
teatcher or something ;-) )

I am targeting a .Net 2.0 frawework essentially with mono and gmcs.
I agree with you about using implicit delegate creation and will use
this syntax in the futur.

Thank you again for your support !


2008/2/23, Chris Howie <cdhowie at gmail.com>:
> On Thu, Feb 21, 2008 at 12:39 PM, Charles-Henri d'Adhémar
>  <cdadhemar at gmail.com> wrote:
>  >  The way a method is attached to an event seems equivalent in class
>  >  Test1 and Test2 below :
>  >
> >                button1.Clicker += new EventHandler(hello_event);
> > [snip]
>  >                button1.Clicker += hello_event;
> >
>  >  Can a method (in our case hello_event) be attached to a GTK# event
>  >  without instantiating a delegate (new EventHandler(hello_event); ) ?
> Yes and no.
>  Actually, the two lines of code you have given above will compile to
>  exactly the same IL sequence.  The ability to "use a method as a
>  delegate" was added in the C# 2.0 language specification as a way to
>  save time coding.  The compiler looks at the context to determine the
>  type it needs (EventHandler in this case) and looks at the right side
>  and says "this is a method with the same or compatible signature as
>  that delegate, let's just create the delegate."  It's similar to type
>  inference in a way.
>  So there are a few points you have to consider:
>  1) Implicitly creating the delegate is easier to type and reads better
>  (in my opinion).
>  2) Implicitly creating the delegate is *NOT* compatible with C# 1.0.
>  Note that mcs does support C# 2.0 features that are binary-compatible
>  with the 1.1 CLI assembly format, which includes features like this
>  one as well as anonymous delegates and the like.  Microsoft's 1.1
>  compiler does not, to my knowledge, support anything but C# 1.0 so if
>  you are targeting the 1.1 framework and would like to be compatible
>  with the MS 1.1 compiler, you should explicitly create the delegate.
>  If you are targeting the 2.0 framework then it makes no difference
>  which you choose in this respect.
>  3) The compiled assembly is going to be identical either way you do
>  it, so there is no runtime performance difference or assembly size
>  difference that will impact your decision.
>  --
>  Chris Howie
>  http://www.chrishowie.com
>  http://en.wikipedia.org/wiki/User:Crazycomputers

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