Visual basic.net Overriding

Overriding

By default, a derived class Inherits methods from its base class. If an inherited property or method needs to behave differently in the derived class it can be overridden; that is, you can define a new implementation of the method in the derived class. The Overridable keyword is used to mark a function as overridable. The keyword Overrides is used to mark that a function is overriding some base class function. Let us see an example.
Import the System namespace (already available in .NET).

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Imports System

Our simple base class:

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Class Human
    'Speak() is declared Overridable
    Overridable Public Sub Speak()
        Console.Writeline ("Speaking")
    End Sub
End Class

Now, let us derive a class from Human:
An Indian is a Human:

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Class Indian
    Inherits Human
    'Let us make Indian speak Hindi, the National Language
    'in India
    'Speak() is overriding Speak() in its base class (Human)
    Overrides Public Sub Speak()
        Console.Writeline ("Speaking Hindi")
    'Important: As you expect, any call to Speak() inside this class
    'will invoke the Speak() in this class. If you need to
    'call Speak() in base class, you can use MyBase keyword.
    'Like this
    'Mybase.Speak()
    End Sub
End Class

Just a class to put our Main().

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Class MainClass
    'Our main function
    Shared Sub Main()
        'Tom is a generic Human
        Dim Tom as Human
        Tom=new Human
        'Tony is a human and an Indian
        Dim Tony as Indian
        Tony=new Indian
        'This call will invoke the Speak() function
        'in class Human
        Tom.Speak()
        'This call will invoke the Speak() function
        'in class Indian
        Tony.Speak()
    End Sub
End Class