Interface vs Abstract Class

Question

Hi Can anyone demonstrate it in detail...Why we use interface rather than abstract class which scenario force us to use interface not abstract class? Thanks

Sujeet Suman · Answer

Mukesh as per my understanding If you have a wide array of subclasses which will be doing largely the same implementation plus extra functionality then you might want an abstract class. It allows you to have many similar objects with fine grained detail. Where as with only interfaces you must have many distinct objects with almost duplicate code. Interfaces have many uses and there is a compelling reason to believe they are 'better'. So finally as per my experience when you have similar kind of implementation then we should go with ABSTRACT class & when you have different kind of implementation and need to maintain some version (your implementation varying time to time. So in that case you can add some new interfaces to your classes.) then we should use INTERFACE. If this is helpful for you then please accept my Answer .

Ravi Patel · Answer

Hi Mukesh checke this link He explained very nicely http://www.c-sharpcorner.com/UploadFile/d0e913/abstract-class-interface-two-villains-of-every-interview/

Priyaranjan K S · Answer

Hi Mukesh An abstract class is a class that you cannot create an instance of. It can provide basic functionality but in order for that functionality to be used one or more other classes must derive from the abstract class. One of the major benefits of abstract classes is that you can reuse code without having to retype it. That has a plethora of benefits such as reducing bugs and making coding faster. A concrete example of an abstract class would be a class called Animal. You see many animals in real life but there are only kinds of animals. That is you never look at something purple and furry and say that is an animal and there is no more specific way of defining it. Instead you see a dog or a cat or a pig... all animals. The point is that you can never see an animal walking around that isn't more specifically something else (duck pig etc.). The Animal is the abstract class and Duck/Pig/Cat are all classes that derive from that base class. Animals might provide a function called Age that adds 1 year of life to the animals. It might also provide an abstract method called IsDead that when called will tell you if the animal has died. Since IsDead is abstract each animal must implement it. So a Cat might decide it is dead after it reaches 14 years of age but a Duck might decide it dies after 5 years of age. The abstract class Animal provides the Age function to all classes that derive from it but each of those classes has to implement IsDead on their own. Now an interface is like an abstract class except it does not contain any logic. Rather it specifies an interface. So there might be an interface called IFly. This might have the methods GoForward and GoDown. Those methods would not actually contain any logic... each class that implements interface IFly would have to implement those GoForward and GoDown methods. You could have classes Duck and Finch implement interface IFly. Then if you want to keep a list of instances that can fly you just create a list that contains items of type IFly. That way you can add Ducks and Finches and any other instance of a class the implements IFly to the list. So abstract classes can be used to consolidate and share functionality while interfaces can be used to specify what the common functionality that will be shared between different instances will be without actually building that functionality for them. Both can help you make your code smaller just in different ways. You can see more detailed example here : http://www.codeproject.com/Articles/11155/Abstract-Class-versus-Interface http://www.c-sharpcorner.com/uploadfile/prasoonk/abstract-class-vs-interface/ Another Good series : http://www.c-sharpcorner.com/UploadFile/d0e913/abstract-class-interface-two-villains-of-every-interview/ http://www.c-sharpcorner.com/UploadFile/d0e913/abstract-class-interface-two-villains-of-every-interview756/ Thanks Priyan If you found this useful Please mark this as Answer