C#自定义控件背景色透明的方法

I struggled for ages with the problem of having controls show through a control that was painted on top of them.  It seems that ControlStyles.SupportsTransparentBackColor just allowed the control to pick up the container's background colour/image and wouldn't prevent the control from hiding any controls that were underneath it. I eventually found an answer so I thought I would post it here.  This code example of a Pointer class, will take an alpha-blended png in the constructor and allow all the controls behind it to show through the transparent or semi-transparent pixels in the png, even when the pointer's location is changed ...

public class Pointer : Control
{
public Pointer(Image image)
: base()
{
Image = image;
SetStyle(ControlStyles.SupportsTransparentBackColor
| ControlStyles.UserPaint
| ControlStyles.AllPaintingInWmPaint
| ControlStyles.Opaque, true);
BackColor = Color.Transparent;
} protected override void OnLocationChanged(EventArgs e)
{
// pick up the container's surface again.
Visible = false;
Visible = true;
} protected override CreateParams CreateParams
{
get
{
CreateParams cp = base.CreateParams;
cp.ExStyle |= 0x00000020; //WS_EX_TRANSPARENT
return cp;
}
} private Image image;
public Image Image
{
get
{
return image;
}
set
{
image = value;
Size = image.Size;
}
} protected override void OnPaint(PaintEventArgs pe)
{
base.OnPaint(pe);
pe.Graphics.DrawImage(image, 0, 0);
} }
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