title: How to allow user to move a control on the form
body: <p>I have a winform on which i want to allow the user to move a control.</p>
  
  <p>The control is (for now) a vertical line : label with border and a width of 1.</p>
  
  <p>The context is not very important but i'll give it to you anyways.  I have a background with some graphics and i'd like the user to be able to slide a guideline above the graphics.  The graphics are made with the NPlots library.  It looks something like this:
  <a href="http://www.ibme.de/pictures/xtm-window-graphic-ramp-signals.png" rel="noreferrer">http://www.ibme.de/pictures/xtm-window-graphic-ramp-signals.png</a></p>
  
  <p>If i can find out how the user can click and drag the label/line control around the screen, i can solve my guideline problem.  Please help.</p>