Is it possible to override a property and return a derived type in VB.NET?

Question

Consider the following classes representing an Ordering system:

Public Class OrderBase
    Public MustOverride Property OrderItem as OrderItemBase
End Class
         


        

Answer 1

You can't do that - it's changing the signature defined on the base. To do what you are trying to do you need to use generics:

Public Class OrderBase(Of T As IOrderItem)
    Public ReadOnly Property OrderItems As IList(Of T)
End Class

My Visual Basic is rusty so hopefully that is accurate...