Visual Basic 2005 for Programmers: Deitel Developer Series, Second Edition

11.9. Wrap-Up

In this chapter we discussed polymorphism, which enables you to “program in the general” rather than “program in the specific,” and we showed how this makes programs more extensible. We began with an example of how polymorphism would allow a screen manager to display several “space” objects. We then demonstrated how base class and derived class references can be assigned to base class and derived class variables. We said that assigning base class references to base class variables is natural, as is assigning derived class references to derived class variables. We then discussed MustOverride methods (methods that do not provide an implementation) and MustInherit classes (abstract classes that typically have one or more MustOverride ...