The method implementation is chosen based on the execution-time type of the object. That's a large part of the point of it. Anyone can use:
public void Foo(Base b)
{
b.VirtualMethod();
}
... and not need to know or care what the execution type is, because polymorphism will take care of it.
I know i can call the Base's virtual method from the derived by calling base.VirtualMethod() but can I call it from outside?
No (at least, not without some horribly hackery to call the virtual method non-virtually), and that's a deliberate part of encapsulation. The overriding implementation has effectively replaced the original implementation for that object.
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