What are abstract classes?

What is Abstract Class?

a)      Classes can be declared as abstract class by using abstract keyword.

b)      Abstract class is designed to act as a base class (to be inherited by other classes).Abstract class is a design concept in program development and provides a base upon which other classes are built.

c)      Abstract class does not allow creating instance or object of it; we must inherit to use it, as in figB.

d)      Abstract classes can have abstract methods as well as non-abstract methods (which must be implemented in the child class).

e)      A non-abstract class derived from an Abstract class must include implementations for all inherited abstract methods.

f)      An abstract class cannot be a sealed or static class.

g)   An abstract method cannot be private, protected or protected internal.

h)      An abstract member cannot be static.