c# 透明panel 示例代码

【核心代码】

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Text;
using System.Windows.Forms;

namespace Nova.Controls.Panel
{
    public class TransparentPanel : Control
    {
        private Color _borderColor;
        private int _borderWidth = 1;
        private DashStyle _borderStyle = DashStyle.Solid;
        private int _opacity = 125;

        public TransparentPanel()
        {

        }

        #region Property
        //[Category("Custom"), Description("Border Color")]
        //public Color BorderColor
        //{
        //    set { _borderColor = value; this.Invalidate(); }
        //    get { return _borderColor; }
        //}

        //[Category("Custom"), Description("Border Width"), DefaultValue(1)]
        //public int BorderWidth
        //{
        //    set
        //    {
        //        if (value < 0) value = 0;
        //        _borderWidth = value;
        //        this.Invalidate();
        //    }
        //    get { return _borderWidth; }
        //}

        //[Category("Custom"), Description("Border Style"), DefaultValue(DashStyle.Solid)]
        //public DashStyle BorderStyle
        //{
        //    set { this._borderStyle = value; this.Invalidate(); }
        //    get { return this._borderStyle; }
        //}

        [Bindable(true), Category("Custom"), DefaultValue(125), Description("背景的透明度. 有效值0-255")]
        public int Opacity
        {
            get { return _opacity; }
            set
            {
                if (value > 255)
                    value = 255;
                else if (value < 0)
                    value = 0;
                _opacity = value;
                this.Invalidate();
            }
        }
        #endregion

        protected override void OnPaintBackground(PaintEventArgs e)
        {
            //do not allow the background to be painted
        }

        protected override CreateParams CreateParams
        {
            get
            {
                CreateParams cp = base.CreateParams;
                cp.ExStyle |= 0x00000020; //WS_EX_TRANSPARENT
                return cp;
            }
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            Graphics g = e.Graphics;
            g.FillRectangle(new SolidBrush(Color.FromArgb(this._opacity, this.BackColor)), this.ClientRectangle);
            base.OnPaint(e);
        }

    }
}