Can't draw on Picturebox
<p>Suppose we have a Form an a picturebox on it: </p>

<p>Where is the problem? Rectangle disapears on picture box. Why?</p>

<pre><code>   private void pictureBox1_Paint(object sender, PaintEventArgs e)
    {
        Graphics gr = pictureBox1.CreateGraphics();
        gr.FillRectangle(Brushes.Red, new Rectangle(10, 10, 50, 50));

    }
</code></pre>
