From the attached snapshot I can tell that you have first added the line series and after that added the bar series. This is the reason that the bar series is on top. If you want the line series on top - simply add the bar series first and then the line series. Alternatively you can set the ZIndex property of the line series to a number that fits your requirement (I think a value of about 260 will suffice).
I am unsure what you mean about the track ball. We have ensured that the track ball is on top of all other elements in the chart and if you have problems with this please give us more information.
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