1. Public Class UndoRedoClass(Of T)
Private UndoStack As Stack(Of T)
Private RedoStack As Stack(Of T)
Public CurrentItem As T
Public Event UndoHappened As EventHandler(Of UndoRedoEventArgs)
Public Event RedoHappened As EventHandler(Of UndoRedoEventArgs)
Public Sub New()
UndoStack = New Stack(Of T)
RedoStack = New Stack(Of T)
End Sub
Public Sub Clear()
UndoStack.Clear()
RedoStack.Clear()
CurrentItem = Nothing
End Sub
Public Sub AddItem(ByVal item As T)
If CurrentItem IsNot Nothing Then UndoStack.Push(CurrentItem)
CurrentItem = item
RedoStack.Clear()
End Sub

2. Public Sub Undo()
RedoStack.Push(CurrentItem)
CurrentItem = UndoStack.Pop()
RaiseEvent UndoHappened(Me, New UndoRedoEventArgs(CurrentItem))
End Sub
Public Sub Redo()
UndoStack.Push(CurrentItem)
CurrentItem = RedoStack.Pop
RaiseEvent RedoHappened(Me, New UndoRedoEventArgs(CurrentItem))
End Sub
Public Function CanUndo() As Boolean
Return UndoStack.Count > 0
End Function
Public Function CanRedo() As Boolean
Return RedoStack.Count > 0
End Function
Public Function UndoItems() As List(Of T)
Return UndoStack.ToList
End Function
Public Function RedoItems() As List(Of T)

3. Return RedoStack.ToList
End Function
End Class
Public Class UndoRedoEventArgs
Inherits EventArgs
Private _CurrentItem As Object
Public ReadOnly Property CurrentItem() As Object
Get
Return _CurrentItem
End Get
End Property
Public Sub New(ByVal currentItem As Object)
_CurrentItem = currentItem
End Sub
End Class