Easiest way to undo drawline

[Codeless]

Is there an "easiest" way to implement undo functionality after drawing a simple line?

 

[Bucky]

If the image is small enough, just store the entire image in a
variable. If you want to undo the action, Dispose of the current
image and set the Graphics object to the old image.

Otherwise you could just draw right over the line with the same
points and thickness, but with a color that matches it with its
background.