Inheritance in VB .Net

Definition

• Inheritance in VB.NET is a fundamental and core concept of object-oriented programming that allows a class (child class or derived class) to inherit fields, properties, methods, and events from another class (parent class or base class). 

Characteristics

• Inheritance promotes code reuse and establishes a relationship between classes.
• By using inheritance, we can create modular, reusable, and extensible code in VB.NET.

Syntax

Class ParentClassName
       ‘ Base class members(data & methods)
End Class

Class ChildClassName
      Inherits ParentClassName
      ‘ Additional members for the derived class (data & methods)
End Class

Inheritance Keywords

• MyBase : This keyword is used to call/represent a base class method or constructor. This is similar to the Super Keyword of Java.
• NotInheritable : This keyword prevents a class from being inherited/supports inheritance. This is similar to Final Class in Java.
• MustInherit : This keyword declares an abstract class that cannot be instantiated but can serve as a base class.

Types of Inheritance

There are the following types of inheritance in VB .Net –

• Single Inheritance

  • A child class inherits from only one parent class and this child class has no further child.

• Multilevel Inheritance

  • A class inherits from a derived class, and this class may have a further child.

• Hierarchical Inheritance

  • When Multiple child classes(have no further children) inherit/derive from a single parent class(have no parent ancestors). 

• Multiple Inheritance

  • VB .Net does not support this inheritance.
  • This inheritance is supported with the help of the Interface concept.

• Hybrid Inheritance

  • Hybrid Inheritance is the combination of two or more types of Inheritance.

Method Overriding

Definition

• Method overriding in VB.NET allows a derived class to provide a specific implementation of a method that is already defined in its base class.

Keywords of Method Overriding

• Overridable and Overrides :

  • For Method overriding, the base class method must be marked as Overridable, and the derived class method must use the Overrides keyword to override it.
  • In other words, The method to be overridden must be marked as Overridable, and the overriding method in the derived class must use the Overrides keyword.

• MustOverride :

  • If the method in the base class is declared with a keyword MustOverride, it must be overridden in the derived class, making the base class as abstract (MustInherit).

• NotOverridable :

  • A method in the base class can be marked as NotOverridable, preventing any derived class from overriding it.

Characteristics

• Method Overriding enables/supports runtime polymorphism, where the method to be executed is determined at runtime based on the object type.
• The overriding method must have the same or greater access level as the base class method.
• By using the method overriding concept, VB.NET enables runtime polymorphism and allows developers to create flexible and extensible object-oriented designs.