Paint on panel allowing auto scroll

Question

I'm implementing an application which want to draw lines in the panel. But the panel must be auto scrolled as it size can be expand at run time. The panel paint method I have used is as below.When I run the program it draws lines, but when I scroll down the panel the lines get crashes.How can I avoid that?

private void panel1_Paint(object sender, PaintEventArgs e)
{
  this.DoubleBuffered = true;
  Pen P = new Pen(Color.Red);

  for (int i = 0; i < 10; i++) {
    e.Graphics.DrawLine(P, (new Point(i * 40, 0)), (new Point(i * 40, 60 * 40)));
  }
  for (int i = 0; i < 60; i++)
  {
    e.Graphics.DrawLine(P, (new Point(0, i  *40)), (new Point(10 * 40, i * 40)));
  }
}

Answer 1

I'll assume that "get crashes" doesn't actually mean that your code crashes. You'll need to offset the drawing by the scroll amount. That's easy to do:

private void panel1_Paint(object sender, PaintEventArgs e) {
  e.Graphics.TranslateTransform(panel1.AutoScrollPosition.X, panel1.AutoScrollPosition.Y);
  // etc
  //...
}