raising events by name

[buu]

So, let's say that a user enters an event name in text box, and would like
to raise it..
is it possible to call events by their 'name'?
Is it possible to enumerate events inside app. and to check their names?

[Marc Gravell]

Is it possible to enumerate events inside app. and to check their names?
Yes; via reflection or System.Componen tModel. This lets you add/remove
event subscriptions, but it doesn't allow you to invoke the event.
Unless you hack about, you only have access to the *public* part of the
event, which (in C# at least) is just the add/remove accessor methods.
The underlying delegate is *often* a private field, but could also be in
an EventHandlerLis t, a Dictionary<,>, or on some parent/child instance.

In short, there is no robust single way of doing this for arbitrary classes.

Marc

[Cor Ligthert[MVP]]

buu,

As a user enters a name in a box, then that is not an event beside the
entering of the data.

The keys used to enter are events, the action done by what is entered has
nothing to do with an event.

You mix up an event by a simple action that you can do with a conditional
operator.

Cor

"buu" <ah*@a.comschre ef in bericht
news:12******** *******@news.vm ware.amis.hr...

So, let's say that a user enters an event name in text box, and would like
to raise it..
is it possible to call events by their 'name'?
Is it possible to enumerate events inside app. and to check their names?

[buu]

I took a wrong example..
but, lets say that I would like to raise up some events wich I know only by
name
"Cor Ligthert[MVP]" <no************ @planet.nlwrote in message
news:11******** *************** ***********@mic rosoft.com...

buu,

As a user enters a name in a box, then that is not an event beside the
entering of the data.

The keys used to enter are events, the action done by what is entered has
nothing to do with an event.

You mix up an event by a simple action that you can do with a conditional
operator.

Cor

"buu" <ah*@a.comschre ef in bericht
news:12******** *******@news.vm ware.amis.hr...

>So, let's say that a user enters an event name in text box, and would
like to raise it..
is it possible to call events by their 'name'?
Is it possible to enumerate events inside app. and to check their names?

[Cor Ligthert[MVP]]

>I took a wrong example..

but, lets say that I would like to raise up some events wich I know only
by name

You are not able to raise up an event, it is something that comes from the
OS.

However normally you can call the method. As you need reflection for this,
then there is mostly something terrible wrong in your program. (Or you
should not have the source anymore and are only able to use the DLL. But
that seems strange to me, how do you then know the name).

Cor

[Cor Ligthert[MVP]]

Buu,

I forgot to tell, some people comming from a scripting envirorment, try when
they first start with real programs, to use the way they used in the
scripting environment. Scripting has the bad habbit that it is slow and less
secure then pre builded exe and dll's.

However, as you real want this, you can create better array's with words,
and with that when they are equal start a method, instead of going the very
slow and insecure method of reflection.

Cor

"buu" <ah*@a.comschre ef in bericht
news:12******** ******@news.vmw are.amis.hr...

>I took a wrong example..
but, lets say that I would like to raise up some events wich I know only
by name
"Cor Ligthert[MVP]" <no************ @planet.nlwrote in message
news:11******** *************** ***********@mic rosoft.com...

>buu,

As a user enters a name in a box, then that is not an event beside the
entering of the data.

The keys used to enter are events, the action done by what is entered has
nothing to do with an event.

You mix up an event by a simple action that you can do with a conditional
operator.

Cor

"buu" <ah*@a.comschre ef in bericht
news:12******* ********@news.v mware.amis.hr.. .

>>So, let's say that a user enters an event name in text box, and would
like to raise it..
is it possible to call events by their 'name'?
Is it possible to enumerate events inside app. and to check their names?

[Jon Skeet [C# MVP]]

Cor Ligthert[MVP] <no************ @planet.nlwrote :

I took a wrong example..
but, lets say that I would like to raise up some events wich I know only
by name

You are not able to raise up an event, it is something that comes from the
OS.

That entirely depends on the event. Look at BindingList<T>. ListChanged,
for example, or the events in my own Push LINQ stuff, or the various
events in ASP.NET.

Conceptually, events have nothing to do with the OS. In a GUI they're
usually tied to something which the operating system has informed the
program about, but that's a very specific example.

However normally you can call the method. As you need reflection for this,
then there is mostly something terrible wrong in your program. (Or you
should not have the source anymore and are only able to use the DLL. But
that seems strange to me, how do you then know the name).

Agreed. The whole point of events is to encapsulate
subscribe/unsubscribe, not raise or replace.

--
Jon Skeet - <sk***@pobox.co m>
Web site: http://www.pobox.com/~skeet
Blog: http://www.msmvps.com/jon_skeet
C# in Depth: http://csharpindepth.com

[Cor Ligthert [MVP]]

Jon

<snip>

Conceptually, events have nothing to do with the OS. In a GUI they're
usually tied to something which the operating system has informed the
program about, but that's a very specific example.

<snip>
Agreed, however invoking an event not direct, is because that you can not
control it direct. I tell it in this way just to make it simple. I knew that
once there would be someone who would tell this was not correct.

:-)

Cor

[Jon Skeet [C# MVP]]

Cor Ligthert [MVP] <no************ @planet.nlwrote :

<snip>

Conceptually, events have nothing to do with the OS. In a GUI they're
usually tied to something which the operating system has informed the
program about, but that's a very specific example.

<snip>
Agreed, however invoking an event not direct, is because that you can not
control it direct. I tell it in this way just to make it simple. I knew that
once there would be someone who would tell this was not correct.

I'm not sure how bringing the OS into the picture unnecessarily (and
incorrectly) makes it simpler though. To my mind it complicates it for
no reason.

--
Jon Skeet - <sk***@pobox.co m>
Web site: http://www.pobox.com/~skeet
Blog: http://www.msmvps.com/jon_skeet
C# in Depth: http://csharpindepth.com

[Dude]

Let me give you a very good example where I need to be able to raise
events by using reflection.

I have an application using another UI system than the one provided by
.Net (In my case, a Flash File processed and displayed by a 3rd party
library).

So I implemented my own GUI classes such as button, textbox, etc. that
map the controls of the Flash UI, and implemented a class that
interfaces the Flash with my GUI classes (call it UIEngine).

When I receive events from that Flash file, the cleanest, most elegant
way of making my GUI classes work would have been to be able to raise
the corresponding events from that UIEngine class, using the event name
provided by the Flash library.

Well, with the actual C#, there is no clean way to do it.

Basically it means:

With C#, you can't make your own UI API, you can't implement your own
'OS' in an elegant way. You need to make this work with a workaround,
from the side, using some methods to raise your events for example,
making C# not so elegant on this aspect, as you are forced to write ugly
code to make your thing work in an elegant way.

C++/CLI allows it. VB.Net allows it. Why not C#?

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