enableMultiSelection property
Enables or disables the multiple data points or series selection.
Defaults to false.
late SelectionBehavior _selectionBehavior;
@override
void initState() {
  _selectionBehavior = SelectionBehavior( enable: true);
  super.initState();
 }
Widget build(BuildContext context) {
    return Container(
        child: SfCartesianChart(
            enableMultiSelection: true,
            series: <BarSeries<SalesData, num>>[
                BarSeries<SalesData, num>(
                  selectionBehavior: _selectionBehavior
                ),
              ],
          )
     );
}
Implementation
final bool enableMultiSelection;