OnPaint method is being call for every child control

Question

I've a UserControl (WinForms, .net 2.0), and I've this:

protected override void OnPaint(PaintEventArgs e)
{
    base.OnPaint(e);

    var rect = e.ClipRectangle;
    var pen = new Pen(Brushes.LightGray, 1);

    e.Graphics.DrawRectangle(pen, rect);
}

I basically want to draw a border on the UserControl, but the rectangle is being draw in all the child controls too! I never read it should be called for every child control, is there a solution?

Answer 1

Because the child controls invalidate the parent, causing this method to be fired for each one.

Instead of using e as the parameter (e is going to be whichever control fired the event, child or not) use the control name explicity.

Answer 2

Why are you using PaintEventArgs.ClipRectangle to determine the bounds of the rectangle? Try using Control.ClientRectangle instead.