C# 简单地在WinForm上放置一个有阴影边框的矩形面板

【实例截图】

【核心代码】

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

namespace ShadowPanel
{
    public class ShadowPanel : Panel
    {
        private Color _panelColor;

        public Color PanelColor
        {
            get { return _panelColor; }
            set { _panelColor = value; }
        }

        private Color _borderColor;

        public Color BorderColor
        {
            get { return _borderColor; }
            set { _borderColor = value; }
        }

        private int shadowSize = 5;
        private int shadowMargin = 2;

        // static for good perfomance 
        static Image shadowDownRight = new Bitmap(typeof(ShadowPanel), "Images.tshadowdownright.png");
        static Image shadowDownLeft = new Bitmap(typeof(ShadowPanel), "Images.tshadowdownleft.png");
        static Image shadowDown = new Bitmap(typeof(ShadowPanel), "Images.tshadowdown.png");
        static Image shadowRight = new Bitmap(typeof(ShadowPanel), "Images.tshadowright.png");
        static Image shadowTopRight = new Bitmap(typeof(ShadowPanel), "Images.tshadowtopright.png");

        public ShadowPanel()
        {

        }

        protected override void OnPaint(PaintEventArgs e)
        {
            base.OnPaint(e);

            // Get the graphics object. We need something to draw with ;-)
            Graphics g = e.Graphics;

            // Create tiled brushes for the shadow on the right and at the bottom.
            TextureBrush shadowRightBrush = new TextureBrush(shadowRight, WrapMode.Tile);
            TextureBrush shadowDownBrush = new TextureBrush(shadowDown, WrapMode.Tile);

            // Translate (move) the brushes so the top or left of the image matches the top or left of the
            // area where it's drawed. If you don't understand why this is necessary, comment it out. 
            // Hint: The tiling would start at 0,0 of the control, so the shadows will be offset a little.
            shadowDownBrush.TranslateTransform(0, Height - shadowSize);
            shadowRightBrush.TranslateTransform(Width - shadowSize, 0);

            // Define the rectangles that will be filled with the brush.
            // (where the shadow is drawn)
            Rectangle shadowDownRectangle = new Rectangle(
                shadowSize   shadowMargin,                      // X
                Height - shadowSize,                            // Y
                Width - (shadowSize * 2   shadowMargin),        // width (stretches)
                shadowSize                                      // height
                );                                    
           
            Rectangle shadowRightRectangle = new Rectangle(
                Width - shadowSize,                             // X
                shadowSize   shadowMargin,                      // Y
                shadowSize,                                     // width
                Height - (shadowSize * 2   shadowMargin)        // height (stretches)
                );

            // And draw the shadow on the right and at the bottom.
            g.FillRectangle(shadowDownBrush, shadowDownRectangle);
            g.FillRectangle(shadowRightBrush, shadowRightRectangle);

            // Now for the corners, draw the 3 5x5 pixel images.
            g.DrawImage(shadowTopRight, new Rectangle(Width - shadowSize, shadowMargin, shadowSize, shadowSize));
            g.DrawImage(shadowDownRight, new Rectangle(Width - shadowSize, Height - shadowSize, shadowSize, shadowSize));
            g.DrawImage(shadowDownLeft, new Rectangle(shadowMargin, Height - shadowSize, shadowSize, shadowSize));

            // Fill the area inside with the color in the PanelColor property.
            // 1 pixel is added to everything to make the rectangle smaller. 
            // This is because the 1 pixel border is actually drawn outside the rectangle.
             Rectangle fullRectangle = new Rectangle(
                1,                                              // X
                1,                                              // Y
                Width - (shadowSize   2),                       // Width
                Height - (shadowSize   2)                       // Height
                );                     
            
            if (PanelColor != null)
            {
                SolidBrush bgBrush = new SolidBrush(_panelColor);
                g.FillRectangle(bgBrush, fullRectangle);
            }

            // Draw a nice 1 pixel border it a BorderColor is specified
            if (_borderColor != null)
            {
                Pen borderPen = new Pen(BorderColor);
                g.DrawRectangle(borderPen, fullRectangle);
            }

            // Memory efficiency
            shadowDownBrush.Dispose();
            shadowRightBrush.Dispose();

            shadowDownBrush = null;
            shadowRightBrush = null;
        }

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