Is it possible to override a property and return a derived type in VB.NET?
- by Casey
Consider the following classes representing an Ordering system:
Public Class OrderBase
Public MustOverride Property OrderItem() as OrderItemBase
End Class
Public Class OrderItemBase
End Class
Now, suppose we want to extend these classes to a more specific set of order classes, keeping the aggregate nature of OrderBase:
Public Class WebOrder
Inherits OrderBase
Public Overrides Property OrderItem() as WebOrderItem
End Property
End Class
Public Class WebOrderItem
Inherits OrderItemBase
End Class
The Overriden property in the WebOrder class will cause an error stating that the return type is different from that defined in OrderBase... however, the return type is a subclass of the type defined in OrderBase. Why won't VB allow this?
