Morten,

   This isn't completely true.

   The drawing will be lost when a repaint is forced.  This can be due to
many factors, not just having the window covered.  You can resize the
window, you can have it covered, a call to invalidate the window could be
made, the display settings could be changed.

   Also, I am curious, what side effects are you getting by using the DC of
a control?  When you override the OnPaint method, or attach to the Paint
event, the DC of the control is exactly what you are getting.

Hi Delme,

Basically, all draing is done using a Graphics object, which can point to
a control, your main form (which is also a control), or a Bitmap image and
so on.

The quick and dirty way to draw using a button event is something like this

// constructor
        public Form1()
        {
            Button b = new Button();
            this.Controls.Add(b);
            b.Click += new EventHandler(b_Click);
        }

// click event method
        void b_Click(object sender, EventArgs e)
        {
            using (Graphics g = this.CreateGraphics())
            {
                g.DrawEllipse(Pens.Black, this.ClientRectangle);
            }
        }

But!!!, you should avoid drawing inside your button event for several
reasons.
1) Any drawing will be lost if someting covers the window.
2) Using the graphics object of a control directly may cause unwanted side
effects

Instead do something like this instead

        bool flag = false;
        void b_Click(object sender, EventArgs e)
        {
            flag = true;
            this.Refresh();
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            if (flag)
                e.Graphics.DrawEllipse(Pens.Black, this.ClientRectangle);
        }

OnPaint will be called each time the window needs to be repainted, like
when it is uncovered.

If you swap 'flag = true' with 'flag = !flag' you show and hide the circle.

Good luck!

On Wed, 23 Aug 2006 14:27:56 +0200, Delme Greening
<this_part_is_rubbish@delme@i-byte.co.uk> wrote: