[alnasser]

كود :

Public Class Form1
   Private urc As New UndoRedoClass(Of String)()
   Private NoAdd As Boolean = False

   Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
       Button_Undo.Enabled = False
       Button_Redo.Enabled = False
       urc.AddItem(RichTextBox1.Text)
   End Sub

   Private Sub Button_Undo_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button_Undo.Click
       NoAdd = True
       urc.Undo()
       RichTextBox1.Text = urc.CurrentItem
       Button_Undo.Enabled = urc.CanUndo
       Button_Redo.Enabled = urc.CanRedo
       NoAdd = False
   End Sub

   Private Sub Button_Redo_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button_Redo.Click
       NoAdd = True
       urc.Redo()
       RichTextBox1.Text = urc.CurrentItem
       Button_Undo.Enabled = urc.CanUndo
       Button_Redo.Enabled = urc.CanRedo
       NoAdd = False
   End Sub

   Private Sub RichTextBox1_TextChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles RichTextBox1.TextChanged
       If Not NoAdd Then
           urc.AddItem(RichTextBox1.Text)
           Button_Undo.Enabled = urc.CanUndo
           Button_Redo.Enabled = urc.CanRedo
       End If
   End Sub
End Class