EventHandling problem : Java has solution but what about Microsoft???

[Herfried K. Wagner [MVP]]

I have added few of the events in some control, example code is:
btnControl.GotFocus +=new EventHandler(EventHandlingMethod);
btnControl.Click +=new EventHandler(EventHandlingMethod);
lblControl.Click +=new EventHandler(EventHandlingMethod);

private void EventHandlingMethod(object sender, EventArgs e)
{
.......
}

btnControl = Button object, lblControl = Lable object

Now the problem is: I am adding the same event handler method in all events
for btnControl and lblControl too.

now in EventHandlingMethod method, i can find which control is using sender
but now if i want to put some switch cases in the method for Event Name then
I have no any such information in the eventargs or anyother way....
=======

I am curious which sense handling different events of different controls in
the same event handler would make. Instead, add separate event handlers for
all event types, not just delegate types. This means separate handlers for
controls' 'Click' and 'GotFocus' events.

 

[Marina]

If you need to do different things depending on the event, why not have different event handlers? You can place common code into a method that both event handlers can call.

I understand what you are saying, but it just doesn't seem like a big deal. It is very easy to work around, and most of the time it is not even an issue because you either need different code in the handler anyway, or the events have different signatures, etc.
Hi,
I have added few of the events in some control, example code is:
btnControl.GotFocus +=new EventHandler(EventHandlingMethod);
btnControl.Click +=new EventHandler(EventHandlingMethod);
lblControl.Click +=new EventHandler(EventHandlingMethod);

private void EventHandlingMethod(object sender, EventArgs e)
{
.......
}

btnControl = Button object, lblControl = Lable object

Now the problem is: I am adding the same event handler method in all events for btnControl and lblControl too.

now in EventHandlingMethod method, i can find which control is using sender but now if i want to put some switch cases in the method for Event Name then I have no any such information in the eventargs or anyother way....

Can someone help/guide me to get the event name?

Is it possible? if yes then how? If no, then any work around?

Thanks in Advance

Regards,
Mahesh Devjibhai Dhola

 

[Mahesh Devjibhai Dhola [MVP]]

Hi,
I have added few of the events in some control, example code is:
btnControl.GotFocus +=new EventHandler(EventHandlingMethod);
btnControl.Click +=new EventHandler(EventHandlingMethod);
lblControl.Click +=new EventHandler(EventHandlingMethod);

private void EventHandlingMethod(object sender, EventArgs e)
{
.......
}

btnControl = Button object, lblControl = Lable object

Now the problem is: I am adding the same event handler method in all events for btnControl and lblControl too.

now in EventHandlingMethod method, i can find which control is using sender but now if i want to put some switch cases in the method for Event Name then I have no any such information in the eventargs or anyother way....

Can someone help/guide me to get the event name?

Is it possible? if yes then how? If no, then any work around?

Thanks in Advance

Regards,
Mahesh Devjibhai Dhola

 

[Andrew Robinson]

Mahesh ,

I agree with what Herfried and Marina have written with regards to different
controls of different types.

The one place where I do find it useful to use a single event handler for
multiple controls is with Button Controls. Take a look at the Button Command
event. You can pass different CommandName and CommandArgument strings for
each button while using the same Button Command event handler.

This works with traditional Button controls as well as Link Buttons and
Image Buttons.

--

Andrew Robinson
www.binaryocean.com
www.bellinghamdotnet.org


Hi,
I have added few of the events in some control, example code is:
btnControl.GotFocus +=new EventHandler(EventHandlingMethod);
btnControl.Click +=new EventHandler(EventHandlingMethod);
lblControl.Click +=new EventHandler(EventHandlingMethod);
private void EventHandlingMethod(object sender, EventArgs e)
{
.......
}
btnControl = Button object, lblControl = Lable object
Now the problem is: I am adding the same event handler method in all events
for btnControl and lblControl too.
now in EventHandlingMethod method, i can find which control is using sender
but now if i want to put some switch cases in the method for Event Name then
I have no any such information in the eventargs or anyother way....
Can someone help/guide me to get the event name?
Is it possible? if yes then how? If no, then any work around?
Thanks in Advance
Regards,
Mahesh Devjibhai Dhola

 

[Mahesh Devjibhai Dhola [MVP]]

Dear,
The Microsoft Event handling framework allows me to do this what you suggest
but some time, its possible to have such requirement so its not the matter
of sense but its my need so if you can suggest me the woraround for my
prolme then it will be helpful to me.

 

[Mahesh Devjibhai Dhola [MVP]]

Dear,
I am creating my own framework and its not centric to Buttton or some
control only. It will be applicable to all the events of all the controls.
So i need one common place which will be a common event handler method for
all and from that method my framework will work ahead by checking the sender
control and event name and i am doing lot other things at event time and i
will need more info than just sender and eventargs so i need to have such
method and switch case for event names.
For the same type of situation, java allows to have event name but i am
wondering why Microsoft has not such a simple provision in EventArgs??

 

[Herfried K. Wagner [MVP]]

The Microsoft Event handling framework allows me to do this what you
suggest
but some time, its possible to have such requirement so its not the matter
of sense but its my need so if you can suggest me the woraround for my
prolme then it will be helpful to me.

No, I can't suggest a workaround, because each workaround would be an ugly
hack I would not want to see getting into production code.

 

[Patrice]

EventArgs is just the base class for event arguments. You could perhaps
define your own class that would pass the information you need.

I won't discuss this design but it looks like you could also inherits from
those controls and change the On<Event> method ?

 

[Danny Tuppeny]

The Microsoft Event handling framework allows me to do this what you suggest
but some time, its possible to have such requirement so its not the matter
of sense but its my need so if you can suggest me the woraround for my
prolme then it will be helpful to me.

It doesn't make sense, but you could create a method called from all
event handlers, eg.

void GlobalHandler(object sender, string command, EventArgs e)
{
// your code here
}

and hook them up like this:

void button1_click(object sender, EventArgs e)
{
GlobalHandler(sender, "Click", e);
}

But I agree with the other posts - it's stupid. If you're doing the same
thing, you wouldn't need the string. If you're doing different things,
they should be in seperate methods.

 

[jmcgrew]

This design seems strange to me too, but I'll take your word that it
makes sense for your project.

This seems like a good time to use C# 2.0's anonymous delegates. If
your event handling method doesn't need to have the standard event
signature, you could do something like this...


private void EventHandlingMethod(string eventName, object sender,
EventArgs e)
{
...
}

btnControl.GotFocus += delegate(object s, EventArgs e) {
EventHandlingMethod("GotFocus", s, e); };
btnControl.Click += delegate(object s, EventArgs e) {
EventHandlingMethod("Click", s, e); };


Now, if you do need to use the standard event signature, you could
create a new EventArgs class that includes a name, stuff the event name
in there, and pass that in as the e parameter:


class NamedEventArgs : EventArgs {
NamedEventArgs(string name, EventArgs inner) { ... }
public string Name { get ... }
public EventArgs InnerArgs { get ... }
}

private void EventHandlingMethod(object sender, EventArgs e)
{
string name;
NamedEventArgs nea = e as NamedEventArgs;
if (nea != null) {
name = nea.Name;
e = nea.Inner;
} else {
name = "???";
}
...
}

btnControl.GotFocus += delegate(object s, EventArgs e) {
EventHandlingMethod(s, new NamedEventArgs("GotFocus", e)); };
btnControl.Click += delegate(object s, EventArgs e) {
EventHandlingMethod(s, new NamedEventArgs("Click", e)); };


Jesse

 

[Mahesh Devjibhai Dhola [MVP]]

Thanks dude,
I am not using .Net 2.0 currently in production environment but i will keep
your solution in my mind.

Thanks for the concern.

 

[John A. Bailo]

You should be looking at multicast delegates as an interface for your
events.

 

[Guest]

Either inherit the controls into a class and override their OnEvent methods
or just put this information in the Control.Tag value... each Control has a
Tag property of type object. However I think having a catch all event handler
is not the solution, but either inheritance of the controls or using the
control tag will work for you.

Chris