Abstract classes and interfaces in C# [duplicate]

Question

Possible Duplicates:
Interface vs Base class
Interface or abstract class?

Hi All,

I am just thinking about the abstract classes and interfaces, I know how they work technically but i don't understand the real use of abstract classes and interfaces. I mean why should we use abstract classes when we know that we can't create it's object, we have to anyway extend this class to use it so why don't we put everything in the derived class.

Same is with interfaces, we have to implement the interface so why don't we put all the methods which are defined in the interface in the class in which we implement the interface.

Can someone please clear my doubts with some examples ?

Answer 1

Links at Stackoverflow

• Exact use of Abstract class
• Interface or abstract class?
• Abstract classes vs Interfaces
• Why do both the abstract class and interface exist in .Net?
• differences between an abstract class and an interface in C#
• What’s the difference between an interface and an abstract class?
• When to use an interface instead of an abstract class and vice versa?
• Help me understand in a practical example the usage abstract classes vs interfaces?

Others

• Abstract Class versus Interface
• Should I use an abstract class or an interface?
• Abstract base class over interface
• Learn This: When to use an Abstract Class and an Interface
• Recommendations for Abstract Classes vs. Interfaces - MSDN
• Working with Abstract classes, Sealed Classes, and Interfaces in C#
• Difference between Abstract class and Interface in C# (.Net)

Answer 2

Also of note, in C# you can only inherit one class but multiple interfaces. An abstract class is a partial implementation of a class with reusable code for multiple subclasses. An interface is just that, an interface to the object for a specific purpose.

A good example would be objects in a game. If the object is Drawable and Collideable you may have common routines to handle that but no common base class, so you have the class implement IDrawable and ICollidable.