Why does this polymorphic C# code print what it does?

Question

I was recently given the following piece of code as a sort-of puzzle to help understand Polymorphism and Inheritance in OOP - C#.

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Answer 1

Easy, you only have to keep the inheritance tree in mind.

In your code, you hold a reference to a class of type 'A', which is instantiated by an instance of type 'C'. Now, to resolve the exact method address for the virtual 'GetName()' method, the compiler goes up the inheritance hierarchy and looks for the most recent override (note that only 'virtual' is an override, 'new' is something completely different...).

That's in short what happens. The new keyword from type 'C' would only play a role if you would call it on an instance of type 'C' and the compiler then would negate all possible inheritance relations altogether. Strictly spoken, this has nothing to do at all with polymorphism - you can see that from the fact that whether you mask a virtual or non-virtual method with the 'new' keyword doesn't make any difference...

'New' in class 'C' means exactly that: If you call 'GetName()' on an instance of this (exact) type, then forget everything and use THIS method. 'Virtual' in contrary means: Go up the inheritance tree until you find a method with this name, no matter what the exact type of the calling instance is.