How to make a listBox semi-transparent?

Question

I tried looking through a few questions on here already but none seemed to fit.

This is what i've tried:

listBox1.BackColor = Color.FromArgb(85, 200, 200, 200);

But at runtime, there's an error. It states that the component doesn't support transparency. I'm asking on here because there could be a workaround. If anyone could help, that'd be great. Thanks in advance!

Answer 1

I suggest going for a ListView in Details View instead.

This is a more modern control, much more powerful and also more supportive when it comes to adding some extra styling..

ListView has a BackgroundImage which alone may be good enough. It doesn't support transparency, though.

But with a few tricks you can make it fake it by copying the background that would shine through..:

void setLVBack(ListView lv)
{
    int alpha = 64;
    Point p1 = lv.Parent.PointToScreen(lv.Location);
    Point p2 = lv.PointToScreen(Point.Empty);
    p2.Offset(-p1.X, -p1.Y );
    if (lv.BackgroundImage != null) lv.BackgroundImage.Dispose();
    lv.Hide();
    Bitmap bmp = new Bitmap(lv.Parent.Width, lv.Parent.Height);
    lv.Parent.DrawToBitmap(bmp, lv.Parent.ClientRectangle);
    Rectangle r = lv.Bounds;
    r.Offset(p2.X, p2.Y);
    bmp = bmp.Clone(r, PixelFormat.Format32bppArgb);
    using (Graphics g = Graphics.FromImage(bmp))
    using (SolidBrush br = new SolidBrush(Color.FromArgb(alpha, lv.BackColor)))
    {
        g.FillRectangle(br, lv.ClientRectangle);
    }
    lv.BackgroundImage = bmp;
    lv.Show();
}

A few notes:

• I hide the listview for a short moment while getting the background pixels
• I calculate an offset to allow borders; one could (and maybe should?) also use SystemInformation.Border3DSize.Height etc..
• I crop the right area using a bitmap.Clone overload
• finally I paint over the image with the background color of the LV, green in my case
• you can set the alpha to control how much I paint over the image
• Also note that I dispose of any previous image, so you can repeat the call when necessary, eg when sizes or positions change or the background etc..
• The ListView overlaps a PictureBox (left) but sits on a TabPage with an image of its own.

Result: