Possible Duplicate:
Shadows vs. Overrides in VB.Net
What's the difference between shadowing a function in a base class in a subclass and overriding the same function? There is performance issues involved too?
I know how to shadow and how to override in VB.net. My question is about when and why should I shadow a function instead override it and vice-versa.
Thanks!
Here is an answer in terms of C#, but I believe that the top explanations are easily understood in terms of VB.Net.
Shadowing in VB.Net is done with "new" in C#, and overriding explicitly uses "override". Let me know if anything else is difficult to understand from the VB.Net point of view.
I haven't found a use for Shadows yet. One difference is that if the method you are overriding / shadowing is called from the base class, if its overwritten the method in the sub class will be called, if its shadowed the base method will still be called (only the sub class knows about the shadowed output).
See the example code, it outputs A,B A
Sub Main()
Dim ClassA As New A
Dim ClassB As New B
Dim ClassC As New C
Console.WriteLine(ClassA.GetText)
Console.WriteLine(ClassB.GetText)
Console.WriteLine(ClassC.GetText)
Console.ReadKey()
End Sub
Public Class A
Public Function GetText()
Return GetSomeText()
End Function
Protected Overridable Function GetSomeText()
Return "A"
End Function
End Class
Public Class B
Inherits A
Protected Overrides Function GetSomeText() As Object
Return "B"
End Function
End Class
Public Class C
Inherits A
Protected Shadows Function GetSomeText()
Return "C"
End Function
End Class
