如何在C＃中清除面板的图形？

Question

I have used grahics in a panel. At start of the program I draw some points in the panel and after that I want to draw lines connecting those points. Problem is when I press tab button the graphics created disappear (but this happens once in the program). Next problem is I want to clear the panel I used following code to clear panel:

Panel1.Invalidate();

But this only clears the lines but not those points that were initially created. Does anyone has a simple solution because I don't want to recreate the panel.

Technical Detail: to draw initial points in panel, paint event of panel1 is used:

Graphics gfx = e.CreateGraphics()

For lines, there is a seprate function that is called on button click and in that I used:

Graphics gfx = Panel1.CreateGraphics();

Another button that is used to clear panel has following code:

Panel1.invalidate();

but it only clears the line graphics, not those initial points.

Answer 1

I was making a mistake by creating initial points in the paint event of panel1. So everytime i call

Panel1.Invalidate();

it recalls that paint event and those points are redrawn and not cleared.

Answer 2

Do you save the points in some sort of collection and draw them in the Paint event?

Then you should empty the collection and then call the Invalidate

Answer 3

The panel is redrawn inside the paint event. It means that you have to draw everything inside this method, instead of accessing the graphics context directly.

This explains why everything you draw when you use Graphics gfx = Panel1.CreateGraphics(); is lost every time the control is redrawn, since during the paint event, you are only drawing the initial points, nothing more.