c# – 在Visual Studio窗体窗体中使用面板上的不透明度的任何技

If true,the control is drawn opaque and the background is not
painted.

>覆盖CreateParams并为其设置WS_EX_TRANSPARENT样式.

Specifies that a window created with this style is to be transparent.
That is,any windows that are beneath the window are not obscured by
the window. A window created with this style receives WM_PAINT
messages only after all sibling windows beneath it have been updated.

>创建一个不透明度属性,该属性接受0到100之间的值,这些值将用作背景的Alpha通道.
>覆盖OnPaint并使用从BackGroundColor和Opacity创建的支持Alpha的画笔填充背景.

完整代码

public class ExtendedPanel : Panel
{
    private const int WS_EX_TRANSPARENT = 0x20;
    public ExtendedPanel()
    {
        SetStyle(ControlStyles.Opaque,true);
    }

    private int opacity = 50;
    [DefaultValue(50)]
    public int Opacity
    {
        get
        {
            return this.opacity;
        }
        set
        {
            if (value < 0 || value > 100)
                throw new ArgumentException("value must be between 0 and 100");
            this.opacity = value;
        }
    }
    protected override CreateParams CreateParams
    {
        get
        {
            CreateParams cp = base.CreateParams;
            cp.ExStyle = cp.ExStyle | WS_EX_TRANSPARENT;
            return cp;
        }
    }
    protected override void OnPaint(PaintEventArgs e)
    {
        using (var brush = new SolidBrush(Color.FromArgb(this.opacity * 255 / 100,this.BackColor)))
        {
            e.Graphics.FillRectangle(brush,this.ClientRectangle);
        }
        base.OnPaint(e);
    }
}

截图