[Syntax rule] A non-abstract base class that implements an interface cannot rely on a derived class for that implementation When a base class implements an interface, it was possible for the class to not implement the methods of the interface if a derived class implemented the methods. The only limitation was that the new constructor method could not be called on the class. Now the compiler requires that every class that implements an interface must have or inherit a complete implementation of every method of the interface. For more information, see X++, C# Comparison: Object Oriented Programming. [Area] 
Interfaces
E s c a p e
E x c e p t i o n s
I n h e r i t a n c e
I n t e r f a c e s
M o d i f i e r s
P a r a m e t e r s
P r e p r o c e s s o r