In C# I know that you can use delegates to assing
multiple addresses of sub and functions to a delegate and
have it fire multiple procedures...
How do I do this in VB? I only know of assigning a
single method to a delegate in VB.NET. I want to use it
as in C#... to fire multiple events.
Thanks in advance!
Nov 20 '05
15  6634 
"IcedCrow" <ch********@aol .com> wrote in news:096701c37e 43$a4dc8590
$a*******@phx.g bl: I glanced through it but could not find an instance of
applying multiple methods to a single delegate, only how
to add a single method to a delegate which i already know
how to do...
AddHandler.
--
Lucas Tam (RE********@rog ers.com)
Please delete "REMOVE" from the e-mail address when replying. http://members.ebay.com/aboutme/coolspot18/
See, now I can comment on this one.
Alright when it comes to multicasts like this yes you want to use AddHandler
as everyone has said.
Now after a lot of research, especially yesterday, the AddHandler keyword is
simply a reference to EventHandlerLis t.AddHandler (object, delegate). At
least thats the way I understand it. And EventHandlerLis t is created at
runtime in most cases it seems. The code for its pretty straight forward
(you can find the source out there) not real complex, but when a delegate is
multicast like this, it automatically calls Delegate.Combin e.
So just use AddHandler.
=)
CJ
"Jay B. Harlow [MVP - Outlook]" <Ja********@ema il.msn.com> wrote in message
news:OA******** ******@TK2MSFTN GP11.phx.gbl... IcedCrow, I understand the combine function, but I'm only working
with one delegate here so there's nothing to combine. Do
I have to create multiple delegate objects that reference
methods and then combine them all? THat seems horribly
ineffecient... You do realize that the "+=" operator in C# when used with delegate types
is shorthand for the Delegate.Combin e function?
While the "-=" operator when used with delegate types is shorthand for
Delegate.Remove function?
You can use ildasm.exe to verify the above statement.
So as I stated, have you tried the Delegate.Combin e function?
Further you do realize that each time you use the AddressOf operator in
VB.NET that you are given a new Delegate?
Hope this helps
Jay
"IcedCrow" <ch********@aol .com> wrote in message
news:00******** *************** *****@phx.gbl.. . Greetings Jay,
No I am not talking about events, I understand how to add
handlers.
I am talking delegates. A delegate object being assigned
the address of a procedure and then having it's invoke
method called to fire that procedure.
In C# I know of how to take a single delegate and assign
to it calls from multiple procedures, so that I only have
to fire off a single INVOKE method from that single
delegate to fire off the multiple methods.
With VB.NET I only know of how to assign a single method
address to a single delegate.
I understand the combine function, but I'm only working
with one delegate here so there's nothing to combine. Do
I have to create multiple delegate objects that reference
methods and then combine them all? THat seems horribly
ineffecient...
I don't know how familiar you are with the MOCs but in
the 2124 C# course they have an example with a nuclear
power plant and one invoke call to a delegate is able to
fire off multiple calls to pump procedures.
This is what I want to do with Visual Basic.NET. It has
nothing to do with events.
Thanks!
Jay,
I completly understand where your coming from on this, and I guess I just
misunderstood what the actual question was. My apologies if I led him in
the wrong direction.
Most often, I like many people automatically associate Delegates with Events
(because its the most common application for them, unelss your doing some
stuff with multi-threading and invoking methods on a parent,sibling, child
control, but usually this is associated with events as well).
So that was my point about talking about AddHandler and hopefully giving a
little insight to this.
Thanks for the clarification and useful code by the way
-CJ
"Jay B. Harlow [MVP - Outlook]" <Ja********@ema il.msn.com> wrote in message
news:u1******** ******@TK2MSFTN GP11.phx.gbl... CJ & Fergus,
The problem is IcedCrow is not using Events, he is using Delegates. A
delegate is a reference to a function. Although Events are implemented in
the terms of a Delegate they are distinct elements.
As far as I can tell AddHandler only works with Events and not with
Delegate variables. (members declared with the Event keyword, not variables
declared with a Delegate type.) I get an error about the delegate variable not
being an Event of the containing class when I attempt to use AddHandler on a
Delegate variable.
I understand he has something like:
Public Delegate Sub MySub()
Public Sub DoWork()
Dim subs As MySub
' magic code to initialize the subs variable
subs.Invoke()
End Sub
Public Sub MyWork()
Debug.WriteLine ("working", "MyWork")
End Sub
Public Sub MyWork1()
Debug.WriteLine ("working", "MyWork1")
End Sub
Public Sub MyWork2()
Debug.WriteLine ("working", "MyWork2")
End Sub
When he uses subs.Invoke in the DoWork sub, he wants all three subs
MyWork, MyWork1, and MyWork2 to be called, the only way I know to do this in
VB.NET is to call Delegate.Combin e itself. Something like:
Public Sub DoWork()
Dim subs As MySub = AddressOf MyWork
Dim sub1 As MySub = AddressOf MyWork1
Dim sub2 As MySub = AddressOf MyWork2
subs = DirectCast([Delegate].Combine(subs, sub1), MySub)
subs = DirectCast([Delegate].Combine(subs, sub2), MySub)
subs.Invoke()
End Sub
Normally I use a Delegate variable when I have a single function to call.
In the above I would probably create a helper function to hide the DirectCast
in a function, cleaning it up significantly.
Public Sub DoWork()
Dim subs As MySub
subs = MakeWork(Addres sOf MyWork, AddressOf MyWork1)
subs = MakeWork(subs, AddressOf MyWork2)
subs.Invoke()
End Sub
Public Function MakeWork(ByVal a As MySub, ByVal b As MySub) As MySub
Return DirectCast([Delegate].Combine(a, b), MySub)
End Function
Hope this helps
Jay
"CJ Taylor" <no****@blowgoa ts.com> wrote in message
news:%2******** ********@TK2MSF TNGP11.phx.gbl. .. See, now I can comment on this one.
Alright when it comes to multicasts like this yes you want to use AddHandler as everyone has said.
Now after a lot of research, especially yesterday, the AddHandler
keyword is simply a reference to EventHandlerLis t.AddHandler (object, delegate).
At least thats the way I understand it. And EventHandlerLis t is created at
runtime in most cases it seems. The code for its pretty straight
forward (you can find the source out there) not real complex, but when a
delegate is multicast like this, it automatically calls Delegate.Combin e.
So just use AddHandler.
=)
CJ
"Jay B. Harlow [MVP - Outlook]" <Ja********@ema il.msn.com> wrote in
message news:OA******** ******@TK2MSFTN GP11.phx.gbl... IcedCrow,
> I understand the combine function, but I'm only working
> with one delegate here so there's nothing to combine. Do
> I have to create multiple delegate objects that reference
> methods and then combine them all? THat seems horribly
> ineffecient...
You do realize that the "+=" operator in C# when used with delegate
types is shorthand for the Delegate.Combin e function?
While the "-=" operator when used with delegate types is shorthand for
Delegate.Remove function?
You can use ildasm.exe to verify the above statement.
So as I stated, have you tried the Delegate.Combin e function?
Further you do realize that each time you use the AddressOf operator
in VB.NET that you are given a new Delegate?
Hope this helps
Jay
"IcedCrow" <ch********@aol .com> wrote in message
news:00******** *************** *****@phx.gbl.. .
> Greetings Jay,
>
> No I am not talking about events, I understand how to add
> handlers.
>
> I am talking delegates. A delegate object being assigned
> the address of a procedure and then having it's invoke
> method called to fire that procedure.
>
> In C# I know of how to take a single delegate and assign
> to it calls from multiple procedures, so that I only have
> to fire off a single INVOKE method from that single
> delegate to fire off the multiple methods.
>
> With VB.NET I only know of how to assign a single method
> address to a single delegate.
>
> I understand the combine function, but I'm only working
> with one delegate here so there's nothing to combine. Do
> I have to create multiple delegate objects that reference
> methods and then combine them all? THat seems horribly
> ineffecient...
>
> I don't know how familiar you are with the MOCs but in
> the 2124 C# course they have an example with a nuclear
> power plant and one invoke call to a delegate is able to
> fire off multiple calls to pump procedures.
>
> This is what I want to do with Visual Basic.NET. It has
> nothing to do with events.
>
> Thanks!
CJ,
Yea sometimes its hard to surmise what the original or the response is
really talking about.
Hey! what I am saying is perfectly clear in my mind! ;-)
Unfortunately sometimes the OP doesn't follow what I am mumbling about...
:-(
I'm just curious to see if we have answered IcedCrow's question.
Jay
"CJ Taylor" <no****@blowgoa ts.com> wrote in message
news:%2******** ********@TK2MSF TNGP11.phx.gbl. .. Jay,
I completly understand where your coming from on this, and I guess I just
misunderstood what the actual question was. My apologies if I led him in
the wrong direction.
Most often, I like many people automatically associate Delegates with
Events (because its the most common application for them, unelss your doing some
stuff with multi-threading and invoking methods on a parent,sibling, child
control, but usually this is associated with events as well).
So that was my point about talking about AddHandler and hopefully giving a
little insight to this.
Thanks for the clarification and useful code by the way
-CJ
<<snip>>
Hi Iced, Jay,
Iced Crow
|| No I am not talking about events, I understand
|| how to add handlers.
|| .........
|| This is what I want to do with Visual Basic.NET.
|| It has nothing to do with events.
Fergus
|| Events blah, blah, AddHandler, blah, blah.
My apologies - brain not in tune with eyes. I didn't give the question the
attention it deserved. :-(
Regards,
Fergus
Hi, try this:
Dim dMyDelegate As MyDelegateSub
dMyDelegate = [Delegate].Combine(Addres sOf DelegSub1, AddressOf DelegSub2)
dMyDelegate.Inv oke()
Also, if you need more than two helpings of delegate, one of the overloads
of the Combine method is an array of delegates.
--
HTH,
-- Tom Spink, Über Geek
Please respond to the newsgroup,
so all can benefit
"Maybe it's a game called 'Punish the User'"
"Iced Crow" <ch********@aol .com> wrote in message
news:79******** *************** *****@phx.gbl.. .
: In C# I know that you can use delegates to assing
: multiple addresses of sub and functions to a delegate and
: have it fire multiple procedures...
:
: How do I do this in VB? I only know of assigning a
: single method to a delegate in VB.NET. I want to use it
: as in C#... to fire multiple events.
:
: Thanks in advance!
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