Dim a As Integer
    Dim b As Integer
    Dim c As Double
 
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button2.Click
        Select Case ComboBox1.Text
            Case "Addieren"
                a = System.Convert.ToInt32(TextBox1())
                b = System.Convert.ToInt32(TextBox2())
                c = a + b
                TextBox3 = c
            Case "Subtrahiern"
                c = a - b
                TextBox3 = c
            Case "Multiplizieren"
                c = a * b
                TextBox3 = c
            Case "Dividieren"
                c = a / b
                TextBox3 = c
            Case Else
                MessageBox.Show("Ungültige Rechenoperation gewählt")
        End Select
    End Sub