Question

I’m not sure that I’m doing the right thing here…

I’m writing a user control that’s supposed to be (fairly) generic. It’s a bit like a modified email client specifically tailored to some of the internal things we do.

The view is composed of two main pieces, a message list and a viewer. I need this viewer to be interchangeable, so if someone wants a different style of view they can simply handle an event and change a property. My original idea was to just have an INoteViewer, but since I’m adding it to my form I also need to guarantee that this object is a Windows.Forms.Control of some sort.

Should I continue along these lines and maybe raise an ArgumentException if I can’t cast it to INoteViewer, or should I go a different direction and create a class that inherits from Windows.Forms.Control?

Answer 1

To do what you want, you could do something like this:

Public Interface IMyInterface
    Sub Method1()
    Sub Method2()

End Interface

Public MustInherit Class MyBaseControl
    Inherits Control
    Implements IMyInterface

    Public MustOverride Sub Method1() Implements IMyInterface.Method1
    Public MustOverride Sub Method2() Implements IMyInterface.Method2
End Class

Public Class MyControl
    Inherits MyBaseControl

    Public Overrides Sub Method1()

    End Sub

    Public Overrides Sub Method2()

    End Sub
End Class

Actually, if you use an abstract class, you might as well not use an interface.