RaiseEvent in inherited classes

Sorry if this is a FAQ: I've read the error notice in help (VS 2005 Visual Basic Express Edition beta 2) saying that I have to "move" the declaration of an event into the class I want to use it in. Doing that means that the

Dim WithEvents myvar As ParentClass

in the MainForm module causes an error because the class doesn't have any events.

My problem is that I want to Dim the parent (mustinherit) class because I want to be able to choose at run time which of two inherited classes I want to use; and I want to use a common routine in the MainForm to display changes in the class.

I've tried declaring this in the child classes:

Public Shadows Event ThingMoved(a as integer etc)

but that prevents any events being raised in the MainForm. Presumably there is a legal way round this... Help

Thanks in advance

Tim Ferguson

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RaiseEvent in inherited classes

Terry Heath
   Protected Overridable Sub OnMyEvent( _
       ByVal e As EventArgs)
     RaiseEvent MyEvent(Me, e)
   End Sub

Wow: that was fast, and just what I needed. Many thanks

Tim

rreineri

You can use a pattern like this:

Public MustInherit Class ParentClass
   Public Event MyEvent(ByVal sender As Object, ByVal e As EventArgs)

   Protected Overridable Sub OnMyEvent(ByVal e As EventArgs)
      RaiseEvent MyEvent(Me, e)
   End Sub
End Class

Public Class ChildClass1
   Inherits ParentClass

   Public Sub SubThatWantsToFireEvent()
      OnMyEvent(EventArgs.Empty)
   End Sub
End Class

Or you could use an interface instead of an abstract (must inherit) base class

Public Interface IEventSource
Event MyEvent(ByVal sender As Object, ByVal e As EventArgs)
End Interface

Public Class ChildClass2
Implements IEventSource

Public Event MyEvent(ByVal sender As Object, ByVal e As System.EventArgs) Implements IEventSource.MyEvent
End Class

Best regards,
Johan Stenberg

RaiseEvent in inherited classes

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