By default, the AllowUndoRedo property is False. Use the AllowUndoRedo property to add Undo/Redo support for operations in the chart. 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 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. Call the Undo method to Undo the last chart operation. The Redo redoes the next action in the chart's redo queue. The UndoRedoQueueLength property gets or sets the maximum number of Undo/Redo actions that may be stored to the chart's queue, or in other words how many operations the chart's Undo/Redo manager may store. 

The Undo/Redo manager of the chart records the following operations:

• exChartUndoRedoMoveBar(0) - "MoveBar;ITEM;KEY;STARTDATEFROM;ENDDATEFROM;STARTDATETO;ENDDATETO"
• exChartUndoRedoParentChangeBar(1), "ParentChangeBar;ITEMOLD;KEY;ITEMNEW"
• exChartUndoRedoAddBar(2) - "AddBar;ITEM;KEY;NAME;STARTDATE;ENDDATE"
• exChartUndoRedoRemoveBar(3) - "RemoveBar;ITEM;KEY;NAME"
• exChartUndoRedoDefineSummaryBars(4) - "DefineSummaryBars;SUMMARYITEM;SUMMARYKEY;ITEM;KEY"
• exChartUndoRedoUndefineSummaryBars(5) - "UndefineSummaryBars;SUMMARYITEM;SUMMARYKEY;ITEM;KEY"
• exChartUndoRedoPercentChange(6) - "PercentChange;ITEM;KEY;OLDVALUE;NEWVALUE"
• exChartUndoRedoAddLink(7) - "AddLink;LINKKEY;STARTITEM;STARTKEY;ENDITEM;ENDKEY"
• exChartUndoRedoRemoveLink(8) - "RemoveLink;LINKKEY"
• exChartUndoRedoGroupBars(9) - "GroupBars;ITEMA;KEYA;STARTA;ITEMB;KEYB;STARTB;GROUPBARSOPTIONS;OPTIONS"
• exChartUndoRedoUngroupBars(10) - "UngroupBars;ITEMA;KEYA;STARTA;ITEMB;KEYB;STARTB"
• exChartUndoUpdateBar(11) - "UpdateBar;ITEM;KEY;PROPERTY;OLDVALUE;NEWVALUE", this can be added only using the StartUpdateBar / EndUpdateBar methods.
• exChartUndoUpdateLink(12) - "UpdateLink;LINKKEY;PROPERTY;OLDVALUE;NEWVALUE", this can be added only using the StartUpdateLink / EndUpdateLink methods.

The ChartStartChanging(exUndo/exRedo) / ChartEndChanging(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 chart. The RedoListAction property lists the Redo actions that can be performed in the chart. 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.

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