Transparency in animator control - wpf

Question

I'm writing a user control for animation.
Its uses an internal ImageList to store the animation images and paint one after the other in a loop.
This is the whole code:
public partial class Animator : UserControl
{
public event EventHandler OnLoopElapsed = delegate { };
private ImageList imageList = new ImageList();
private Timer timer;
private bool looping = true;
private int index;
private Image newImage;
private Image oldImage;
public Animator()
{
InitializeComponent();
base.DoubleBuffered = true;
timer = new Timer();
timer.Tick += timer_Tick;
timer.Interval = 50;
}
public bool Animate
{
get { return timer.Enabled; }
set
{
index = 0;
timer.Enabled = value;
}
}
public int CurrentIndex
{
get { return index; }
set { index = value; }
}
public ImageList ImageList
{
set
{
imageList = value;
Invalidate();
index = 0;
}
get { return imageList; }
}
public bool Looping
{
get { return looping; }
set { looping = value; }
}
public int Interval
{
get { return timer.Interval; }
set { timer.Interval = value; }
}
private void timer_Tick(object sender, EventArgs e)
{
if (imageList.Images.Count == 0)
return;
Invalidate(true);
index++;
if (index >= imageList.Images.Count)
{
if (looping)
index = 0;
else
timer.Stop();
OnLoopElapsed(this, EventArgs.Empty);
}
}
protected override void OnPaintBackground(PaintEventArgs e)
{
if (oldImage != null)
e.Graphics.DrawImage(oldImage, ClientRectangle);
else
e.Graphics.Clear(BackColor);
}
protected override void OnPaint(PaintEventArgs e)
{
Graphics g = e.Graphics;
if (imageList.Images.Count > 0)
{
newImage = imageList.Images[index];
g.DrawImage(newImage, ClientRectangle);
oldImage = newImage;
}
else
{
e.Graphics.Clear(BackColor);
}
}
}
The animation seems very nice and smooth,
but the problem is that its surrounding rectangle is painted black.
What am I missing here?
I've seen very smooth transparent animation done here in WPF,
I've placed some label behind it and they are seen thru the rotating wheel as I hoped.
But I don't know WPF well enough to build such a control in WPF.
Any idea or WPF sample code will be appreciated.

Answer 1

This was solved by removing this line from the constructor:
base.DoubleBuffered = true;
Now the control is fully transparent, even while changing its images.