Call the Undo method to Undo the last chart operation. The Undo method have effect only if the AllowUndoRedo property is True. The CTRL+Z performs the last undo operation, while the CTRL+Y redoes the next action in the chart's Redo queue. The Redo redoes the next action in the chart's redo queue.  The CanUndo property retrieves a value that indicates whether the chart may perform the last Undo operation. The CanRedo property retrieves a value that specifies whether the chart can execute the next operation in the chart's Redo queue. The ChartStartChanging(exUndo/exRedo) / ChartEndChanging(exUndo/exRedo) event notifies your application whenever an Undo/Redo operation is performed. 

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

• "AddBar;ITEMINDEX;KEY", indicates that a new bar has been created
• "RemoveBar;ITEMINDEX;KEY", indicates that a bar has been removed
• "MoveBar;ITEMINDEX;KEY", indicates that a bar has been moved or resized
• "PercentChange;ITEMINDEX;KEY", indicates that the bar's percent has been changed
• "UpdateBar;ITEMINDEX;KEY", indicates that one or more properties of the bar has been updated (ItemBar property, this operation can be added only using the StartUpdateBar / EndUpdateBar methods)
• "ParentChangeBar;ITEMINDEX;KEY", indicates that the bar's parent has been changed
• "GroupBars;ITEMINDEXA;KEYA;STARTA;ITEMINDEXB;KEYB;STARTB", specifies that two bars has been grouped
• "UngroupBars;ITEMINDEXA;KEYA;STARTA;ITEMINDEXB;KEYB;STARTB", specifies that two bars has been ungrouped
• "DefineSummaryBars;SUMMARYITEMINDEX;SUMMARYKEY;ITEMINDEX;KEY", indicates that a bar has been defined as a child of a summary bar
• "UndefineSummaryBars;SUMMARYITEMINDEX;SUMMARYKEY;ITEMINDEX;KEY", indicates that a bar has been removed from the summary bar's children
• "AddLink;KEY", indicates that a new link has been created
• "RemoveLink;KEY", indicates that a link has been removed
• "UpdateLink;KEY", specifies that one of more properties of the link has been updated (Link property, this operation can be added only using the StartUpdateLink / EndUpdateLink methods)

The records of the Undo/Redo queue may contain actions in the following format (available starting from 23.0):

• "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 UndoListAction property lists the Undo actions that can be performed in the chart. Use the UndoRemoveAction method to remove the last actions from the undo queue.