使用Paint事件重画GroupBox来修改边框颜色

在.Net下进行WinForm开发，GroupBox是经常要用到的一个控件。但是GroupBox自身的边框是灰白色的，其样式很难令开发者满意。在不借用第三方控件的情况下，通过其的Paint事件对GroupBox进行重画，也可以很方便的修改其边框颜色/样式。

　　简要说一下实现思路。首先用Clear方法清除GroupBox的显示，接着再用合适的样式把GroupBox画出来。把GroupBox拆分为4个圆角，一行标题文字和数段直线等元素，把这些元素摆放在合适的位置，拼凑出GroupBox的外框。定义4个Rectangle（用于后面的画圆角），确定它们的大小和位置；然后在确切的位置上画4个弧段，按圆角在GroupBox上的位置确定其角度；接着在对应的位置画出GroupBox标题和几条直线，就大功告成了。只需简单修改代码中的设置颜色语句，便可以完成GroupBox边框颜色的更换了。

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Drawing.Drawing2D;

using System.Text;

using System.Windows.Forms;

  

namespace WindowsApplication2

{

    public partial class Form1 : Form

    {

        public Form1()

        {

            InitializeComponent();

        }

  

        private void groupBox1_Paint(object sender, PaintEventArgs e)

        {

            e.Graphics.Clear(groupBox1.BackColor);

  

            Rectangle Rtg_LT = new Rectangle();

            Rectangle Rtg_RT = new Rectangle();

            Rectangle Rtg_LB = new Rectangle();

            Rectangle Rtg_RB = new Rectangle();

            Rtg_LT.X = 0; Rtg_LT.Y = 7; Rtg_LT.Width = 10; Rtg_LT.Height = 10;

            Rtg_RT.X = e.ClipRectangle.Width - 11; Rtg_RT.Y = 7; Rtg_RT.Width = 10; Rtg_RT.Height = 10;

            Rtg_LB.X = 0; Rtg_LB.Y = e.ClipRectangle.Height - 11; Rtg_LB.Width = 10; Rtg_LB.Height = 10;

            Rtg_RB.X = e.ClipRectangle.Width - 11; Rtg_RB.Y = e.ClipRectangle.Height - 11; Rtg_RB.Width = 10; Rtg_RB.Height = 10;

  

            Color color = Color.FromArgb(51, 94, 168);

            Pen Pen_AL = new Pen(color, 1);

            Pen_AL.Color = color;

            Brush brush = new HatchBrush(HatchStyle.Divot, color);

  

            e.Graphics.DrawString(groupBox1.Text, groupBox1.Font, brush, 6, 0);

            e.Graphics.DrawArc(Pen_AL, Rtg_LT, 180, 90);

            e.Graphics.DrawArc(Pen_AL, Rtg_RT, 270, 90);

            e.Graphics.DrawArc(Pen_AL, Rtg_LB, 90, 90);

            e.Graphics.DrawArc(Pen_AL, Rtg_RB, 0, 90);

            e.Graphics.DrawLine(Pen_AL, 5, 7, 6, 7);

            e.Graphics.DrawLine(Pen_AL, e.Graphics.MeasureString(groupBox1.Text, groupBox1.Font).Width + 3, 7, e.ClipRectangle.Width - 7, 7);

            e.Graphics.DrawLine(Pen_AL, 0, 13, 0, e.ClipRectangle.Height - 7);

            e.Graphics.DrawLine(Pen_AL, 6, e.ClipRectangle.Height - 1, e.ClipRectangle.Width - 7, e.ClipRectangle.Height - 1);

            e.Graphics.DrawLine(Pen_AL, e.ClipRectangle.Width - 1, e.ClipRectangle.Height - 7, e.ClipRectangle.Width - 1, 13);

        }

    }

}