Drawing a single guideline over several NPlots or alternative solution

Question

I am using NPlot charting library to draw several plots illustrating signal fluctuations. The plots are inserted one beneath the other in a flowlayoutpanel1. The x axis is the time. The y is the value of the signal. I've added a trackbar at the bottom, along the x axis. When the user moves the trackbar, the value of each signal is displayed somewhere (in relation to the trackbar's position).

All of this is already functional.

I've been asked to add some visual way to illustrate the precise time where the trackbar is. They want some sort of vertical line that would move with the trackbar, over all the Nplots. However they are open to alternatives.

I have tried drawing the line but it's difficult to draw in relation to the trackbar's position. Also it ends up being drawn BEHIND the Nplots.

I've also tried drawing a static grid on the flowpanel but the Nplots are not transparent, and my boss doesn't like each plot having a individual grid for aesthetic purposes.

At this point i'm open to any "out-of-the-box" suggestions, or corrections on my implementation. I'm self taught in C# so i haven't done anything like this before.

Please help!

EDIT: I have gotten something slightly better by using a label with a border, stretching it to be tall and having width of 1. This creates a Line that goes over all other control. Now my biggest challenge is calculating the position of the trackbar pointer to make the line match it...

Answer 1

After a lot of fiddling, i found that the only way to have a line drawn over all other controls was NOT to use the Graphics drawline, as the controls placed on top were not transparent and i could not access their graphics component (was a imported control not a .NET class).

I ended up going with the EDIT solution, took a label with a border and put the width to 1, creating a simple line instead of a box.

The position formula took a lot of fine tuning, the way to go was to calculate (estimate) the width between two trackbar ticks an add a tiny offset for the control itself. Using the traback's pointer Value property, i could calculate the position of the label/line so that it would follow the trackbar pointer. There is a minuscule offset sometimes formed but not well seen to the naked eye.