Hello, Bartholomeo, thank you for the reply.
I know about ChartTrackBallBehavior, but it only works on mouse hover, while I wanted the same for mouse click.
So that after user clicks somewhere on chart, hairpin stays at that point and does not move after the mouse. Some event is fired and we can get X value on server side. When data is added to chart, hairpin stays at the same X point.
Maybe it is possible to add such kind of property to ChartTrackBallBehavior in future releases.