how to turn off a public member in a derived class

[csvax]

Hi All,

I have two class A and B. A is a base class and B is derived from A. My question is how to make a public member in A invisible in B. For example,
Class A
public property p1() as string
Get
....
End Get
Set
......
End Set
End Class
Class B
inherits A
< put some code to turn off p1 >
End Class

for Class B, there is no B.p1. How can i do that ? Thanks.

[Cander]

make it Protected instead of Public in the base class

[csvax]

Thanks Cander. You are right. But in my case, it has to be a public property in A so that it can be used by the functions dealing with class A. But for the functions dealing with class B, i want to hide the p1. Any suggestions ?

[Cander]

protected will still let class b call the function in class a...it just wont be visible to anyone instancing class b.

[csvax]

Thanks again, Cander . Yes, i understand how protected works. But my problem is like below:

Dim clsA as ClassA
Dim clsB as ClassB

1: clsA.p1 = ...
2: clsB.p1= ...

i want to only 1: be legal operation not 2:

[Cander]

hmmm
try Protected Friend

[Cander]

nevermind that wont work either.

[hellswraith]

Can you make the property overridable? Then in Class B, override it but make it private that way it isn't visible to the user and it would be illegal to use it.

That is theory, I can't run the test right now to see if that would work (don't have .Net on this machine).

[Pirate]

what about including NotInheritable Keyword in your A Class.I've not tried it but just a thought crossed my mind

[DevGrp]

But in my case, it has to be a public property in A so that it can be used by the functions dealing with class A. But for the functions dealing with class B, i want to hide the p1. Any suggestions ?

Make it private. The functions in class A will still have access to it.

[Hu Flung Dung]

What about something like this:

public class MyClassA

     Public Property Whatever
         ...
      End Property

End Class

Public Class MyClassB
           inherits MyClassA

           Private Shadows Property Whatever
             ...
           End Property

End Class

I havn't tried it yet, but I'm 99% sure it will work.

EDIT:

Never mind. It doesn't work (darn).

However, it just occured to me, that you really shouldn't be allowed to do this. Inheritance, by definition, allows derived classes to work exactly the same way as their base classes. If certain members have a different scope in derived classes, you completely lose that compatibility. (Example: I often pass a Bitmap object to the Graphics.drawImage procedure, eventhough drawImage accepts only the Image object. Since Bitmap is inherited from Image, I can often use them interchangably).

[Pirate]

Originally posted by DevGrp
Make it private. The functions in class A will still have access to it.

but that way he can't call the function from the class.

[CornedBee]

Hu Flung Dung is right. The OOP philosophy subset used in .Net doesn't allow this.

In C++ you could do it by deriving protected or private:

class B : protected A
{
};

but that isn't possible in the CLS.