Re: Multiple level base calls
From: Bruce Wood (brucewood_at_canada.com)
Date: 02/21/05
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Date: 21 Feb 2005 09:54:43 -0800
Hmmm... code with no explanation, and it's code that doesn't even
compile!
I understand the implication: that declaring PrintMe() in classes A, B,
and C will cause "Original A" to print out if you cast a reference of
type "C" to type "A". I assume that you meant to say that:
C a = new C();
//Invoking Class C Method
MessageBox.Show(a.PrintMe());
//Casting with Class A Method
MessageBox.Show(((A)a).PrintMe());
will display two message boxes: one that says, "Overridden C" and the
next that says, "Original A". Unfortunately, if you had tried to
compile this code, you would have found that it wouldn't, because you
must make A's PrintMe "virtual", and specify either "override" or "new"
on B and C's PrintMe.
The behaviour you are claiming will happen only if you declare the
PrintMe methods in B and C to be "new". "new," however, isn't an
override, so you won't get the polymorphic behaviour that the OP wants.
If you were to specify "override," you would get the behaviour that the
OP wants, but both message boxes would display "Overridden C." That, in
a nutshell, was the OP's problem: how to have both message boxes
display "Overridden C," but then go back to call the base method
("Original A") on demand.
Unfortunately, no can do (in C#).
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