Pl. help me to understand this code (hiding)?

murali 0

I saw this code in one of the notes. class A { public virtual void MyName() {Console.Writeline("My Name is A");} } class B:A { public override void MyName() {Console.Writeline("My Name is B");} } class C:B { public new virtual void MyName() {Console.Writeline("My Name is C");} } class D:C { public override void MyName() {Console.Writeline("My Name is D");} } C c = new D(); c.MyName(); //---------->prints "My name is D" A a = new D(); a.MyName(); //---------->prints "My name is B" ?????????? I thought a.MyName() should print "My name is D". Can any one explain why?. Any notes on hiding/Dynamic binding on the web/books? Thanks

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murali 022y ago
Thanks for your explanation. A a = new D(); Here 'a' is a object of the class D of the type A (???) . I thought, whenever a method of object 'a' is called, it calls the method of class D. Thanks again.
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ssswamii22y ago
A a = new D(); So you have a D object masquerading as an A object. When you call a.MyName, it's going to go down the vtable. It sees A.MyName, but it is virtual, so it'll lookup any overrides (it will NOT look up any 'new' implementations of the function using the new keyword). It goes down and finds that B overrides it, so it uses B's implementation. Now it will look to see if there are any overrides of B's implementation. Are there? No, C does not override. So it stops right there, which is why it prints B's implementation (My name is B). Does that make sense to you? The key here is overriding - the new keyword does NOT override an implementation. To discover the answer to problems like these, it's as seimple as going down the list of inheritors until you find the bottom-most override.
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