C# How to Draw a Rubber Band Selection Rectangle on Panel, like one used in Windows Explorer?

Question

I have one Flow Layout Panel with some User Controls in it. I Want to Select these controls using rectangle selection using Mouse,like one used in windows file explorer . I have tried these : https://support.microsoft.com/en-us/kb/314945 But it was very flickering and not useful (I might be wrong,please correct me). Any good examples please.

Answer 1

Drawing the rubber-band rectangle is done like this:

private void panel1_MouseMove(object sender, MouseEventArgs e)
{
    if (e.Button == System.Windows.Forms.MouseButtons.Left)
    {
        panel1.Refresh();
        using (Graphics g = panel1.CreateGraphics())
        {
            Rectangle rect = GetRectangle(mdown, e.Location);
            g.DrawRectangle(Pens.Red, rect);
        }
    }

}

private void panel1_MouseDown(object sender, MouseEventArgs e)
{
    mdown = e.Location;
}

It uses a helper function:

static public Rectangle GetRectangle(Point p1, Point p2)
{
    return new Rectangle(Math.Min(p1.X, p2.X), Math.Min(p1.Y, p2.Y),
        Math.Abs(p1.X - p2.X), Math.Abs(p1.Y - p2.Y));
}

I don't get any flicker from it. If you do, maybe you have coded the Paint event, you may want to use a double-buffered Panel :

class DrawPanel : Panel 
{
   public DrawPanel()
    {
        DoubleBuffered = true;
    }
}

---

Update: Instead of a Panel , which is a Container control and not really meant to draw onto, you can use a Picturebox or a Label (with Autosize=false ); both have the DoubleBuffered property turned on out of the box and support drawing better than Panels do.

Answer 2

If the problem is the flickering only. You might want to set the Forms double buffer property to true.