A class definition can reference properties, methods, or events only when they are defined in the class or in one of its superclasses.

To reference a property, method, or event of this class:

• Fix the code on the indicated line if the property, method, or event has been defined in the class.

• Define the property, method, or event in the class if the property, method, or event has not been defined.

If you want to use a property or method in this class but you want subclasses to provide its implementation, declare the property or method as an Abstract property or method in this class.