継承の基本

オーバーライドは、基本クラスでOverridable（オーバーライドできるよ：意訳）して 派生クラスでOverrides（オーバーラードするよ：意訳）すればいい。 やっかいなのがコンストラクタNewで基本クラスにNewがあり、派生クラスにもNewがあるとオーバーライドされずに、それぞれが実行されるらしい（試していない）

https://docs.microsoft.com/ja-jp/dotnet/visual-basic/programming-guide/language-features/objects-and-classes/inheritance-basics

Const BonusRate As Decimal = 1.45D
Const PayRate As Decimal = 14.75D

Class Payroll
   Overridable Function PayEmployee(
       ByVal HoursWorked As Decimal,
       ByVal PayRate As Decimal) As Decimal
       PayEmployee = HoursWorked * PayRate
   End Function
End Class



Class BonusPayroll
   Inherits Payroll
   Overrides Function PayEmployee(
       ByVal HoursWorked As Decimal,
       ByVal PayRate As Decimal) As Decimal
       ' The following code calls the original method in the base
       ' class, and then modifies the returned value.
       PayEmployee = MyBase.PayEmployee(HoursWorked, PayRate) * BonusRate
   End Function
End Class



Sub RunPayroll()
   Dim PayrollItem As Payroll = New Payroll
   Dim BonusPayrollItem As New BonusPayroll
   Dim HoursWorked As Decimal = 40
   MsgBox("Normal pay is: " &
       PayrollItem.PayEmployee(HoursWorked, PayRate))
   MsgBox("Pay with bonus is: " &
       BonusPayrollItem.PayEmployee(HoursWorked, PayRate))
End Sub