program 22: abstract class

 program to demonstrate concept of abstract and not inheritable class.

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Imports System.Console

Module Module1

    Public MustInherit Class abstractclass

        Public MustOverride Function add() As Integer

        Public MustOverride Function mul() As Integer

    End Class

    Public Class abstractone

        Inherits abstractclass

        Dim i As Integer = 20

        Dim j As Integer = 30

        Public Overrides Function add() As Integer

            Return i + j

        End Function

        Public Overrides Function mul() As Integer

            Return i * j

        End Function

    End Class

    Sub Main()

        Dim a As New abstractone

        WriteLine("sum is:" & a.add())

        WriteLine("multiplication is:" & a.mul())

        ReadKey()

    End Sub

End Module
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codestrew