[Mono-list] Base class casting weirdness

Daniel Lewis dihlewis@yahoo.co.uk
Thu, 17 Jan 2002 01:13:11 +0000 (GMT)


I wonder if anyone can shed light on this. In C#, the 'base' keyword is
used to access methods and constructors of base classes:

class A {
	public virtual string Foo () { return "A"; }

class B : A {
	public override string Foo () { return base.Foo (); }

Invoking Foo on an instance of B returns "A", as you'd expect. The C#
programmer's reference that is packaged with the SDK states that:

	base.Foo ()

.. called in an instance method of B is exactly equivalent to writing:

	((A)this).Foo ()

And that in fact this is what the compiler replaces it with at compile
time.  But if you try to implement it this way:

	public override string Foo () { return ((A)this).Foo (); }

CSC will compile it, but you'll get a StackOverflowException at runtime.
Why would I want to write it this way instead of using 'base'? Well, I've
got a class C derived from B, that wants to implement Foo by invoking A's
definition. Can anyone think of a way to do this? Is the runtime
exception correct, or is this an SDK bug? And what does MCS/Mono do with


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