Kind of event overriding

  • Thread starter Thread starter Marius Horak
  • Start date Start date
M

Marius Horak

I have an object that works with an external treeview
(myObject.TreeView = formTreeView)
On myObject.TreeView = formTreeView assigment an AftreSelect event is
being attached inside the object code.
The problem is that formTreeView may have its AfterSelect event that
will be executed before myObject AtferSelect when I want it to be
executed after.

But how to do it?


MH
 
Marius Horak said:
I have an object that works with an external treeview
(myObject.TreeView = formTreeView)
On myObject.TreeView = formTreeView assigment an AftreSelect event is
being attached inside the object code.
The problem is that formTreeView may have its AfterSelect event that
will be executed before myObject AtferSelect when I want it to be
executed after.

But how to do it?
Click to expand...

You can't.

The whole point of events as compared to public delegates is that you can't
mess with them from outside the class. If this wasn't the case you would
have a massive security hole.

You'll have to rethink your design - possibly derive your own class from
TreeView and create a new event to fire first.
 
Marius,

You can't control the order of event processing. The idea behind this design
pattern is that you don't care and basically don't know how many listeners
you have, thus you don't care about the order of execution.

There are different design patterns such us "Chain of Responsibility" where
you can guarantee the order of execution.
 
Nick said:
You can't.
Click to expand...

I must say this is a major overlook on a part of M$.
The whole point of events as compared to public delegates is that you
can't mess with them from outside the class. If this wasn't the case
you would have a massive security hole.
Click to expand...

I don't agree with a such approach.
Either I'm in control or I'm being controled by some stupid rules.
possibly derive your own class from TreeView
Click to expand...

The best way to get into a mess.

MH
 
Marius Horak said:
I must say this is a major overlook on a part of M$.
Click to expand...

I don't think that you will find anyone to agree with you.
I don't agree with a such approach.
Either I'm in control or I'm being controled by some stupid rules.
Click to expand...

You are in control of YOUR classes - why should you have control over
someone else's class that they don't want to give you?

As I said it is POSSIBLE to use a public multicast delegate (either as a
field or a property) instead of an event. In this case the user of your
class could add,remove or rearrange the order of delegate invocation at
will.
The best way to get into a mess.
Click to expand...

No - it's quite straightforward: all events in the framework are fired from
virtual methods called "On..." . You just need to override the appropriate
method and raise your own event before calling the base implementation to
raise the original event.
 
Marius,

This is not overlook at all. This is the way this design patern is defined
and has to work.
 
Nick said:
I don't think that you will find anyone to agree with you.
Click to expand...

Well, in such case M$ went mad when they made the KeyPress event public.
Can you imagine the mess one can create in an application when a user
types for example FCUK as a company name?

MH
 
Stoitcho said:
This is not overlook at all. This is the way this design patern is
defined and has to work.
Click to expand...

Yes, yes, The Big Brother knows better what I want.

MH
 
Marius Horak said:
Yes, yes, The Big Brother knows better what I want.
Click to expand...

No - the big brother knows better what MOST people using C# want and
security comes high on the list.

BB neither knows nor cares what you as an individual want especially as,
according to your email address, your are nobody :-)
 
Nick said:
No - the big brother knows better what MOST people using C# want and
security comes high on the list.
Click to expand...

There is no such thing as "security" for developers (just for end
users), this is just a tool limitation.
If a developer wants to do something he/she should be able to do it.
Remember, those stupid computers are here to serve people.

Security? Which system do you prefer when crossing a road?

German, where can cross a road only in selected places and you have to
wait for a green light or face penalty

or

UK, where you can cross a road at any place and time, but watch the
traffic before crossing.


Most of the progress was made by people who took a risk (even when they
had to break a rule or two).

MH

(e-mail address removed) -> EU is one big con and due to stupid rules sooner or
later everyone will be "nobody" in EU. EU rules will control your life
(using computers and M$ software)
 
Marius Horak said:
There is no such thing as "security" for developers (just for end
users), this is just a tool limitation.
Click to expand...

Developers are also users of other developers libraries.
If a developer wants to do something he/she should be able to do it.
Remember, those stupid computers are here to serve people.
Click to expand...

You can do something stupid. But why do you expect MS ti help you? They are
busy enough doing their own stupid things :-)
Security? Which system do you prefer when crossing a road?

German, where can cross a road only in selected places and you have to
wait for a green light or face penalty

or

UK, where you can cross a road at any place and time, but watch the
traffic before crossing.
Click to expand...

The analogy is not a good one - in neither case is your security enforced in
the same sense as we are talking about - they penalize breach of rules
rather than make it impossible - A better analogy would be a pedestrian
footbridge with no access to the road at all.
Most of the progress was made by people who took a risk (even when they
had to break a rule or two).
Click to expand...

We are not talking about rules here - If it was just a rule then you would
have just broken it and not posted a question.

If you want to take risks then write in C++ not C#.
MH

(e-mail address removed) -> EU is one big con and due to stupid rules sooner or
later everyone will be "nobody" in EU. EU rules will control your life
(using computers and M$ software)
Click to expand...

I can't argue with that :-(

P.S. We are in the wrong group here anyway - it should be the csharp one.
 
If a developer wants to do something he/she should be able to do it.

If you want it you should go ahead and implement it. The framework and the
languages gives you everything to do it.
 
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