By default, the AllowUndoRedo property is false, which indicates that the Undo/Redo feature us disabled. 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 added three elements 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. 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:

• "AddElement;ELEMENTID", indicates that a new element has been created
• "RemoveElement;ELEMENTID", indicates that an element has been removed
• "MoveElement;ELEMENTID", indicates that an element has been moved or resized
• "UpdateElement;ELEMENTID", indicates that one or more properties of the element has been updated, using the StartUpdateElement / EndUpdateElement methods
• "AddLink;LINKID", indicates that a new link has been created
• "RemoveLink;LINKID", indicates that a link has been removed
• "UpdateLink;LINKID", specifies that one of more properties of the link has been updated, using the StartUpdateLink / EndUpdateLink methods

Also, the Undo/Redo queue may include:

• "StartBlock", specifies that a block of operations begins (initiated by StartBlockUndoRedo method)
• "EndBlock", specifies that a block of operations ends (initiated by EndBlockUndoRedo method)

The LayoutStartChanging(exUndo/exRedo) / LayoutEndChanging(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.

The control's toolbar displays the Undo/Redo commands if the ToolBarFormat property includes 103, Undo (undoes the last control operation, enabled only if the Undo operation is possible) and 104, Redo (redoes the next action in the control's redo queue, enabled only if the Undo operation is possible) identifiers as in the following screen shot:

The Undo/Redo toolbar-commands are automatically enabled or disabled