The Undo method undoes the last control operation. The AllowUndoRedo property enables or disables the Undo/Redo feature. The CanUndo method indicates whether the control can perform an Undo 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
• "AddPool;POOLTID", indicates that a new pool has been created
• "RemovePool;POOLTID", indicates that a pool has been removed
• "MovePool;POOLID", indicates that a pool has been moved or resized
• "UpdatePool;POOLID", indicates that one or more properties of the pool has been updated, using the StartUpdatePool / EndUpdatePool 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.