Programa que asigna una definitiva de notas - Con clases

Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        If (ComboBox1.SelectedIndex) = 0 Then

            Dim cli As New POO

            cli.codigo = InputBox("digite codigo")

            cli.NOTA_1 = InputBox("digite nota_1")

            cli.NOTA_2 = InputBox("digite nota_2")

            cli.NOTA_3 = InputBox("digite nota_3")

            cli.cali_poo()

            cli.mostrar()

        Else

            Dim cli_m As New BD

            cli_m.codigo = InputBox("digite codigo")

            cli_m.n_1 = InputBox("digite nota_1")

            cli_m.n_2 = InputBox("digite nota_2")

            cli_m.cali_BD()

            cli_m.mostrar()

        End If

    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        ComboBox1.Items.Add("ASIGNATURA POO")

        ComboBox1.Items.Add("ASIGNATURA DB")

    End Sub

End Class

Se utilizan 3 clases

Public Class ASIGNATURA

    Public codigo As Integer

    Public def As Integer

    Sub mostrar()

        MessageBox.Show(CStr(def), "definitiva", MessageBoxButtons.OK, MessageBoxIcon.Information)

    End Sub

End Class

Public Class BD

    Inherits ASIGNATURA

    Public n_1 As Integer

    Public n_2 As Integer

    Sub cali_BD()

        def = ((n_1 * 0.2) + (n_2 * 0.8))

    End Sub

End Class

Public Class POO

    Inherits ASIGNATURA

    Public NOTA_1 As Integer

    Public NOTA_2 As Integer

    Public NOTA_3 As Integer

    Sub cali_poo()

        def = ((NOTA_1 + NOTA_2 + NOTA_3) / 3)

    End Sub

End Class

Programa hecho en visual studio

lenguaje:  .net