How Do I Get an Object to Listen For its Property's Event?

Question

I have an object of type SomeObject, with an event StatusChanged.

I have a property in SomeObject of type Status also with an event StatusChanged.

Within a private function in SomeObject, I would like to run some logic (including firing the StatusChanged event) in the event that Status has fired its StatusChanged event. I have been away from events for a while so it's a bit cloudy to me. How do I do this?

I'm writing in ASP.NET/VB.NET

Thanks :)

EDIT Ok, in the event that I can't do the above, how would I get the outer object (SomeObject) to fire its StatusChanged event when the inner object (Status) fires its StatusChanged event?

Answer 1

Events don't work that way. You can't perform logic based on whether an event has been fired. You can only write logic that takes place when an event is fired.

---

Ok, here's an attempt. It's been a while since I've done this in VB.NET, though:

Public Enum CurrentStatus
    Good
    Bad
End Enum

Public Class StatusEventArgs
    Inherits EventArgs
    Private _currentStatus As CurrentStatus

    Public Property CurrentStatus() As CurrentStatus
        Get
            Return _currentStatus
        End Get
        Set(ByVal value As CurrentStatus)
            _currentStatus = value
        End Set
    End Property
End Class

Public Class StatusClass
    Public Event StatusChanged As EventHandler(Of StatusEventArgs)

    Protected Overridable Sub OnStatusChanged(ByVal newStatus As CurrentStatus)
        Dim s As New StatusEventArgs()
        s.CurrentStatus = newStatus
        RaiseEvent StatusChanged(Me, s)
    End Sub
End Class

Public Class SomeClass
    Private _status As StatusClass
    Public Event StatusChanged As EventHandler(Of StatusEventArgs)

    Protected Overridable Sub OnStatusChanged(ByVal newStatus As CurrentStatus)
        Dim s As New StatusEventArgs()
        s.CurrentStatus = newStatus
        RaiseEvent StatusChanged(Me, s)
    End Sub

    Public Property Status() As StatusClass
        Get
            Return _status
        End Get
        Set(ByVal value As StatusClass)
            If Not _status Is Nothing Then
                RemoveHandler _status.StatusChanged, AddressOf StatusHandler
            End If

            _status = value

            If Not _status Is Nothing Then
                AddHandler _status.StatusChanged, AddressOf StatusHandler
            End If
        End Set
    End Property

    Private Sub StatusHandler(ByVal sender As Object, ByVal e As StatusEventArgs)
        OnStatusChanged(e.CurrentStatus)
    End Sub
End Class