Hi Pedram,
We recently uploaded a SP of the control which imlements build in X / Y line intersection - to find the y values of a XY scatter line you can now use:

List<NVector2DD> intersections = someLineSeries.IntersectWithXValue(someXValue);

Let us know if you meet any problems or have any questions.

Best Regards,
Nevron Support Team

Is there a built it in tool or suggested method to finding Y value at a particular X value from a XY Line chart using the X-axis cursor position?

For example we have time on the X axis, and we have several Line Series on the chart. Our data sets are in the hundreds of thousands for each series.