Why should i use abstract class?

Hi,

1. An abstract class is the one that is not used to create objects.
2. An abstract class is designed to act as a base class (to be inherited by other classes).
3. Abstract class is a design concept in program development and provides a base upon which other classes are built.
4. Abstract classes are similar to interfaces.
5. After declaring an abstract class, it cannot be instantiated on it's own, it must be inherited.
6. Like interfaces, abstract classes can specify members that must be implemented in inheriting classes. Unlike interfaces, a class can inherit only one abstract class.
7. Abstract classes can only specify members that should be implemented by all inheriting classes.

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Hi Maheswar,


Abstract classes are useful when creating components because they allow you specify an invariant level of functionality in some methods, but leave the implementation of other methods until a specific implementation of that class is needed. They also version well, because if additional functionality is needed in derived classes, it can be added to the base class without breaking code.



Thanks

An abstract class can in fact do a lot more than an interface: 

1. It can contain non-abstract instance methods and properties.

2. It can contain static methods and properties.

3. It can contain instance and static fields.

4. It can contain constants, operators and nested classes or structs.

5. Members don't necessarily have to be public, they can be internal, protected or private as well.

Of course, the drawback of abstract classes is that you can only inherit from one of them, whereas you can implement multiple interfaces as well as inherit from a single non-abstract class.