By default, the AllowUndoRedo property is False. The Undo and Redo features let you remove or repeat single or multiple actions, but all actions must be undone or redone in the order you did or undid them – you can’t skip actions. For example, if you change the value of three cells in an item and then decide you want to undo the first change you made, you must undo all three changes. To undo an action you need to press Ctrl+Z, while for to redo something you've undone, press Ctrl+Y. Setting the AllowUndoRedo property, clears the previously undo-redo queue. If the AllowUndoRedo property is True, the CTRL+Z performs the last undo operation, while the CTRL+Y redoes the next action in the control's Redo queue. The CanUndo property retrieves a value that indicates whether the control may perform the last Undo operation. The CanRedo property retrieves a value that specifies whether the control can execute the next operation in the control's Redo queue. Call the Undo method to Undo the last control operation. The Redo redoes the next action in the control's redo queue. The UndoRedoQueueLength property gets or sets the maximum number of Undo/Redo actions that may be stored to the control's queue, or in other words how many operations the control's Undo/Redo manager may store. 

The records of the Undo/Redo queue may contain actions in the following format:

• "AddItem;ITEMINDEX", indicates that a new item has been created
• "RemoveItem;ITEMINDEX", indicates that an item has been removed
• "ChangeItemPos;ITEMINDEX", indicates that an item changes its position or / and parent
• "ChangeCellValue;ITEMINDEX;CELLINDEX", indicates that the cell's value has been changed
• "ChangeCellState;ITEMINDEX;CELLINDEX", indicates that the cell's state has been changed

Also, the Undo/Redo queue may include:

• "StartBlock", specifies that a block of operations begins
• "EndBlock", specifies that a block of operations ends

The URChange(exUndo/exRedo) event notifies your application whenever an Undo/Redo operation is performed. The UndoListAction property lists the Undo actions that can be performed in the control. The RedoListAction property lists the Redo actions that can be performed in the control. Use the UndoRemoveAction method to remove the last actions from the undo queue. The RedoRemoveAction method removes the first action to be performed if the Redo method is invoked.