Vista - Icommand

>From the Expressions interactive designer there is a Csharp example
which I have put thru a VB converter - I am stuck on the following
(last) error triggered by Implements ICommand

Hope some one can help with a simple line of code , have spent sometime
already on the rest of the stuff,
Thanks
Casey

Error--
Error 4 Class 'DelegateCommand' must implement 'Event
CanExecuteChanged(sender As Object, e As EventArgs)' for interface
'System.Windows.Input.ICommand'.

Source---
Imports System
Imports System.Windows.Input
Namespace Awdataclass

'''
''' DelegateCommand is a simplified version of WPF's ICommand. You
can wrap one of these around any method,
''' and thus bind any Command on any WPF object to your method.
'''
''' DelegateCommand also supports an IsEnabled property you can use
to turn the command on and off.
'''
Public NotInheritable Class DelegateCommand

Implements ICommand
' Type signature of the method that DelegateCommand works with
- returns void, no arguments.
Public Delegate Sub SimpleEventHandler()

' Remember the method so we can call it when it's time.
Private handler As SimpleEventHandler

' Maintain our enabled state.
Private isEnabled_Renamed As Boolean = True

' Simple constructor: Just pass in the method that needs to be
called when the command executes.
Public Sub New(ByVal handler As SimpleEventHandler)
Me.handler = handler
End Sub

#Region "ICommand implementation"

' Executing the command is as simple as calling that method we
were handed on creation.
Private Sub Execute(ByVal arg As Object) Implements
ICommand.Execute
Me.handler()
End Sub

' Saying whether we can execute the command.
Private Function CanExecute(ByVal arg As Object) As Boolean
Implements ICommand.CanExecute
Return Me.IsEnabled
End Function

' This is the event that WPF's command architecture listens to
so it knows when to update the UI
' on command enable/disable.
Public Event CanExecuteChanged As EventHandler
#End Region

' Public visibility of our isEnabled flag - note that when it
is set, we need to raise the event
' so that WPF knows to update any UI that uses this command.
Public Property IsEnabled() As Boolean
Get
Return Me.isEnabled_Renamed
End Get
Set(ByVal value As Boolean)
Me.isEnabled_Renamed = value
Me.OnCanExecuteChanged()
End Set
End Property

' Simple event propagation that makes sure someone is listening
to the event before raising it.
Private Sub OnCanExecuteChanged()
If Not Me.CanExecuteChangedEvent Is Nothing Then
RaiseEvent CanExecuteChanged(Me, EventArgs.Empty)
End If
End Sub
End Class
End Namespace