when to use abstract class and when to use interface in c#

Question

Possible Duplicates:
interface and abstract class.
Abstract classes vs Interfaces

Can anyone tell me when one should use an abstract class and when one should use an interface with sample scenarios?

See: http://stackoverflow.com/questions/1474249/abstract-classes-vs-interfaces — Goran Jovic, Feb 10 '11 at 18:49
Lots of duplicates here. http://stackoverflow.com/questions/2987253/interface-vs-abstract-class for example. — Justin Morgan, Feb 10 '11 at 18:52

score 3 · Answer 1 · answered Feb 10 '11 at 18:48

3

You should use an abstract class if you need to supply a base implementation.

Otherwise, use an interface.

answered Feb 10 '11 at 18:48

SLaks

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anyway, this is a straightforward great answer. – Caspar Kleijne Feb 10 '11 at 18:57

score 3 · Accepted Answer · answered Feb 10 '11 at 18:49

3

If you're defining behavior (like IEnumerable, since a List acts like an IEnumerable), then use an interface, but if you're defining a kind of object (an IS-A) relationship, use an abstract class (like Stream -- since a MemoryStream IS-A Stream).

answered Feb 10 '11 at 18:49

user541686

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score 2 · Answer 3 · answered Feb 10 '11 at 18:48

When you want to provide an implementation of a method/set of methods but don't want people to directly instantiate your parent class, use an Abstract Class.

If you want to define what members a class must interface, but not provide any implementation, use an Interface.

when to use abstract class and when to use interface in c#

3 Answers3