重绘panel控件，实现panel的阴影效果

最近想在项目中添加一个要有阴影的panel控件，找了好多资料，最后通过采用图片的方式实现了panel的阴影效果，效果图如下：

重绘代码如下：

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

namespace ShadowPanel3
{
    public partial class UserPanel : Panel
    {
        public UserPanel()
        {

        }
            /// <summary>
        /// 字段和属性 ， panel的颜色
        /// </summary>
        private Color _panelColor;
        public Color PanelColor 
        {
            get { return _panelColor; }
            set { this._panelColor = value; }
        }

        /// <summary>
        /// 字段和属性，border的颜色
        /// </summary>
        private Color _borderColor;
        public Color BorderColor
        {
            get { return _borderColor; }
            set { this._borderColor = value; }
        }

        /// <summary>
        /// 阴影区域大小
        /// </summary>
        private int shadowSize = 5;

        //将预备的小图标转化
        static Image shadowDownRight = new Bitmap(typeof(UserPanel), "Images.tshadowdownright.png");
        static Image shadowDown = new Bitmap(typeof(UserPanel), "Images.tshadowdown.png");
        static Image shadowRight = new Bitmap(typeof(UserPanel), "Images.tshadowright.png");
        static Image shadowTop = new Bitmap(typeof(UserPanel),"Images.tshadowtop.png");
        static Image shadowLeft = new Bitmap(typeof(UserPanel),"Images.tshadowleft.png");
        static Image shadowLeftDown = new Bitmap(typeof(UserPanel),"Images.tshadowleftdown.png");
        static Image shadowLeftTop = new Bitmap(typeof(UserPanel),"Images.tshadowlefttop.png");
        static Image shadowTopLeft = new Bitmap(typeof(UserPanel),"Images.tshadowtopleft.png");

        /// <summary>
        /// 重绘panel
        /// </summary>
        /// <param name="e"></param>
        protected override void OnPaint(PaintEventArgs e)
        {
            base.OnPaint(e);
            //Get the graphics object. We need something to draw with 
            Graphics g = e.Graphics;

            //下边和右边画笔
            TextureBrush shadowRightBrush = new TextureBrush(shadowRight,WrapMode.Tile);
            TextureBrush shadowDownBrush = new TextureBrush(shadowDown,WrapMode.Tile);

            //上边和左边画笔
            TextureBrush shadowLeftBrush = new TextureBrush(shadowLeft, WrapMode.Tile);
            TextureBrush shadowTopBrush = new TextureBrush(shadowTop,WrapMode.Tile);

            //给画笔定位
            shadowDownBrush.TranslateTransform(0, Height - shadowSize);
            shadowRightBrush.TranslateTransform(Width - shadowSize, 0);

            shadowTopBrush.TranslateTransform(0,0);
            shadowLeftBrush.TranslateTransform(0,0);

            //每个阴影区域非配一个矩形区域
            Rectangle shadowDownRectangle = new Rectangle(
                shadowSize,                                                     //X
                Height-shadowSize,                                         //Y
                Width-shadowSize*2,                                     //width(stretches)           
                shadowSize                                                    //height
                );

            Rectangle shadowRightRectangle = new Rectangle(
              Width-shadowSize,                                           //X
              shadowSize,                                                     //Y
              shadowSize,                                                    //width         
              Height-shadowSize*2                                       //height(stretches)  
              );

            Rectangle shadowTopRectangle = new Rectangle(
              shadowSize,                                                    //X
              0,                                                                     //Y
              Width-shadowSize*2,                                       //width         
              shadowSize                                                     //height(stretches)  
              );

            Rectangle shadowLeftRectangle = new Rectangle(
              0,                                                                    //X
              shadowSize,                                                    //Y
              shadowSize,                                                    //width         
              Height-shadowSize*2                                       //height(stretches)  
              );

            //在底部和右边画出阴影
            g.FillRectangle(shadowDownBrush,shadowDownRectangle);
            g.FillRectangle(shadowRightBrush,shadowRightRectangle);
            //在上部和左边画出阴影
            g.FillRectangle(shadowTopBrush,shadowTopRectangle);
            g.FillRectangle(shadowLeftBrush,shadowLeftRectangle);

            //四个角落处的阴影
            g.DrawImage(shadowDownRight, new Rectangle(Width-shadowSize, Height-shadowSize,shadowSize,shadowSize));
            g.DrawImage(shadowLeftDown, new Rectangle(0, Height - shadowSize, shadowSize, shadowSize));
            g.DrawImage(shadowLeftTop, new Rectangle(0, 0, shadowSize, shadowSize));
            g.DrawImage(shadowTopLeft, new Rectangle(Width-shadowSize, 0, shadowSize, shadowSize));


            Rectangle fullRectangle = new Rectangle(
                1,
                1,
                Width - (shadowSize + 2),
                Height - (shadowSize + 2)
                );

            if (PanelColor != null)
            {
                SolidBrush bgBrush = new SolidBrush(_panelColor);
                g.FillRectangle(bgBrush,fullRectangle);
            }

            //给panel添加边框颜色
            if (_borderColor != null)
            {
                Pen borderPen = new Pen(BorderColor);
                g.DrawRectangle(borderPen,fullRectangle);
            }

            //释放画笔资源
            shadowDownBrush.Dispose();
            shadowRightBrush.Dispose();
            shadowLeftBrush.Dispose();
            shadowTopBrush.Dispose();

            shadowDownBrush = null;
            shadowRightBrush = null;
            shadowTopBrush = null;
            shadowLeftBrush = null;
        }

            //Correct resizing
            protected override void OnResize(EventArgs e)
            {
                base.Invalidate();
                base.OnResize(e);
            }
    }
}