Inheritance establishes common behavior and interfaces for your classes, while composition ... and “has a” rule when designing your types. Prefer using composition over inheritance when ...

An abstract class is a special type of class that cannot ... In addition, you must use an interface if you want to simulate inheritance for structs, because they can’t actually inherit from ...

Classes with clear responsibilities, well-defined boundaries and a proper inheritance ... declared using the sealed keyword, followed by the permits clause to explicitly name the classes that can ...

Extension methods provide a great way for extending a class functionality -- but it's interfaces that let you use those ... "You don't screw with working code." And, unlike using inheritance to extend ...