Hiding inherited method

[Guest]

I was trying to break some polymorphism, expecting it not to work, but I'm a
curious sort.

I was seeing what happens when a derived class tries to hide an inherited
method with a private new method, expecting an error or warning; I got
neither with the result that the inherited method does _not_ get hidden (i.e.
not possibe to break polymorphism/inheritance this way, yay!)

My question then is, why is there no warning that the code may not work the
way the writer expects? Is it simply because the _new_ keyword turns it off?
Without the _new_ keyword, the warning about hiding fires, but this is a case
where no hiding will happen anyway, because the private method _does_not_
hide the inherited method.

 

[Jon Skeet [C# MVP]]

I was trying to break some polymorphism, expecting it not to work, but I'm a
curious sort.

I was seeing what happens when a derived class tries to hide an inherited
method with a private new method, expecting an error or warning; I got
neither with the result that the inherited method does _not_ get hidden (i.e.
not possibe to break polymorphism/inheritance this way, yay!)

My question then is, why is there no warning that the code may not work the
way the writer expects? Is it simply because the _new_ keyword turns it off?
Without the _new_ keyword, the warning about hiding fires, but this is a case
where no hiding will happen anyway, because the private method _does_not_
hide the inherited method.

Well, it hides it within that class - it just doesn't hide it for other
users of the class.

 

[Bob Milton]

And, by casting the derived object to the base class, I can even call
the "hidden" method!
Bob

 

[Jon Skeet [C# MVP]]

And, by casting the derived object to the base class, I can even call
the "hidden" method!

Absolutely - but that's always true with "hiding", as anything else
would break Liskov's Substitution Principle.

 

[Bob Milton]

True. But it still amazes me how many people want to be able to
eliminate a public function in the base class (which in essence you can't
really do).
Bob

 

[Jon Skeet [C# MVP]]

True. But it still amazes me how many people want to be able to
eliminate a public function in the base class (which in essence you can't
really do).

Absolutely. Like regular expressions, I regard inheritance as a
powerful tool which is unfortunately overused. See

http://msmvps.com/jon.skeet/archive/2006/03/04/inheritancetax.aspx

for a more detailed rant