Interface vs Base class

Question

When should I use an interface and when should I use a base class?

Should it always be an interface if I don\'t want to actually define a base implementation of the

Answer 1

Regarding C#, in some senses interfaces and abstract classes can be interchangeable. However, the differences are: i) interfaces cannot implement code; ii) because of this, interfaces cannot call further up the stack to subclass; and iii) only can abstract class may be inherited on a class, whereas multiple interfaces may be implemented on a class.