Hide an event in an inherited class

bobo jede

Hi, I have an interesting problem (interesting for me :)). I need to hide an event in an inherited class. Example: Base class: ComboBox Inherited class: MyCombo And I want the event SelectedIndexChanged to be "disabled" out of MyCombo class. So that it shloud be impossible to write: MyCombo mc = new MyCombo(); mc.SelectedIndexChanged += new EventHandler(mc_SelectedIndexChanged); I tried this: **private new** event EventHandler SelectedIndexChanged; but it doesn't work - it is still possible to use this event. Is there any way to do this? And is it correct to do it in OOP? Thanx, Bobo

Ed Poore

I havn't heard of a way to do this, maybe you could mark the event as Obsolete?

Formula 1 - Short for "F1 Racing" - named after the standard "help" key in Windows, it's a sport where participants desperately search through software help files trying to find actual documentation. It's tedious and somewhat cruel, most matches ending in a draw as no participant is able to find anything helpful. - Shog9 Ed

J4amieC

bobo.jede wrote:

Is there any way to do this?

Yes, write your own control, rather than inheriting ComboBox.

bobo.jede wrote:

And is it correct to do it in OOP?

Quite simply, no it is not. Inheritance implies that the derived object inherits every public property/method/event from its parent.

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bobo jede

You mean Obsolete attribute? I've tried it, but it didn't help :( Thanx for your answer Bobo

bobo jede

J4amieC wrote:

Yes, write your own control, rather than inheriting ComboBox.

Yes, that can be a way :) but I want to use this control and it's rich functionality.

J4amieC wrote:

Quite simply, no it is not. Inheritance implies that the derived object inherits every public property/method/event from its parent.

But I can do the same with methods, don't I ?! Bobo

J4amieC

bobo.jede wrote:

But I can do the same with methods, don't I

No, you can never completly hide a method in a derived class either. I suppose you could 'new' it and just do nothing within the method, but its still there.

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leppie

Try overriding OnSelectedIndexChanged and DONT call the base class.

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bobo jede

Perhaps I understand what you mean, but this doesn't "disable" calling SelectedIndexChanged event. It seems that it is not possible to do, what I want and that it is not correct in OOP principles. Bobo

Ed Poore

bobo.jede wrote:

You mean Obsolete attribute?

Yes

bobo.jede wrote:

I've tried it, but it didn't help

I know it won't but it informs other developers that you shouldn't use it. Maybe if you mark it with this and then in the event throw a NotImplementedException. The obsolete gives them the reason why they should not use it. The only (and best way) to do this would be to write your own control (NB you don't have to write it from scratch you could create a wrapper around an existing ComboBox, only exposing the methods / events / properties you want).

Formula 1 - Short for "F1 Racing" - named after the standard "help" key in Windows, it's a sport where participants desperately search through software help files trying to find actual documentation. It's tedious and somewhat cruel, most matches ending in a draw as no participant is able to find anything helpful. - Shog9 Ed

Andrew Lygin

Make your new event public and use ObsoleteAttribute with two parameters. In this case compiler will return an error when somebody try to use this event.

[Obsolete("SelectedIndexChanged is obsolete. Use MyNewEvent instead.", true)]
public new event EventHandler SelectedIndexChanged;