List (Of T) & HashSet (Of T) Provides Notifications When Items Added or Removed



Public Class ObservableList(Of T)
   Inherits List(Of T)

#Region " Constructor "

   Public Sub New()

   End Sub

#End Region

#Region " Property "

   Public ReadOnly Property InnerList As IEnumerable(Of T)
       Get
           Return MyBase.ToList.AsReadOnly
       End Get
   End Property

#End Region

#Region " Method "

   Public Overloads Sub Add(item As T)
       If Not Me.InnerList.Contains(item) Then
           MyBase.Add(item)
           Me.OnChanged(item, ObservableChangeAction.Add)
       End If
   End Sub

   Public Overloads Sub Remove(item As T)
       If Me.InnerList.Contains(item) Then
           MyBase.Remove(item)
           Me.OnChanged(item, ObservableChangeAction.Remove)
       End If
   End Sub

   Protected Sub OnChanged(item As T, action As ObservableChangeAction)
       RaiseEvent Changed(Me, New ObservableEventArgs(CType(item, Object), action))
   End Sub

#End Region

#Region " Event "

   Public Event Changed As EventHandler(Of ObservableEventArgs)

#End Region

End Class ' ObservableList(Of T(




Public Class ObservableHashSet(Of T)
   Inherits HashSet(Of T)

#Region " Constructor "

   Public Sub New()

   End Sub

#End Region

#Region " Property "

   Public ReadOnly Property InnerList As IEnumerable(Of T)
       Get
           Return MyBase.ToList.AsReadOnly
       End Get
   End Property

#End Region

#Region " Method "

   Public Overloads Sub Add(item As T)
       If MyBase.Add(item) Then
           Me.OnChanged(item, ObservableChangeAction.Add)
       End If
   End Sub

   Public Overloads Sub Remove(item As T)
       If MyBase.Remove(item) Then
           Me.OnChanged(item, ObservableChangeAction.Remove)
       End If
   End Sub

   Protected Sub OnChanged(item As T, action As ObservableChangeAction)
       RaiseEvent Changed(Me, New ObservableEventArgs(CType(item, Object), action))
   End Sub

#End Region

#Region " Event "

   Public Event Changed As EventHandler(Of ObservableEventArgs)

#End Region

End Class ' ObservableHashSet(Of T(




Public Class ObservableEventArgs
   Inherits EventArgs

   Public Sub New(item As Object, changeAction As ObservableChangeAction)
       Me.Item = item
       Me.ChangeAction = changeAction
   End Sub

   Public Property Item As Object
   Public Property ChangeAction As ObservableChangeAction

End Class ' ObservableEventArgs




Public Enum ObservableChangeAction
   Add
   Remove
End Enum



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