I know this question had been asked more than a few times, but so far I haven\'t been able to find a good solution for it.
I\'ve got a panel with other control on it
I think the best way is to inherit the control of which you want to draw a line on. Override the OnPaint method, call base.Paint() from within, after that draw the line using the same graphic instance. At the same time, you can also have a parameter which specific at which point the line should be draw, so that you can control the line directly from your main form.