C# GDI在控件上绘图

以在chart控件上和窗体上画矩形为例子

using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Linq;using System.Text;using System.Windows.Forms;using System.IO;using System.Configuration;namespace WFApp2{    public partial class data : Form    {        public data()        {            InitializeComponent();            //窗体            g = this.CreateGraphics();            //chart控件            g2 = this.chart1.CreateGraphics();        }                         public Point firstPoint = new Point(0, 0);  //鼠标第一点         public Point secondPoint = new Point(0, 0);  //鼠标第二点         public bool begin = false;   //是否开始画矩形         /// <summary>        /// 在from上画矩形        /// </summary>        Graphics g;        /// <summary>        /// 在chart1控件上画矩形        /// </summary>        Graphics g2;        /// <summary>        /// 在窗体上按下鼠标事件        /// </summary>        /// <param name="sender"></param>        /// <param name="e"></param>        private void data_MouseDown(object sender, MouseEventArgs e)        {            begin = true;            firstPoint = new Point(e.X, e.Y);        }        /// <summary>        /// 在窗体上鼠标移动开始绘图        /// </summary>        /// <param name="sender"></param>        /// <param name="e"></param>        private void data_MouseMove(object sender, MouseEventArgs e)        {            if (begin)            {                //清除窗体绘图面,相当于刷新了一次窗体界面然后重新绘制                g.Clear(this.BackColor);                //获取新的右下角坐标                 secondPoint = new Point(e.X, e.Y);                //获取两个数中的大者或小者                int minX = Math.Min(firstPoint.X, secondPoint.X);                int minY = Math.Min(firstPoint.Y, secondPoint.Y);                int maxX = Math.Max(firstPoint.X, secondPoint.X);                int maxY = Math.Max(firstPoint.Y, secondPoint.Y);                //画框                 g.DrawRectangle(new Pen(Color.Red), minX, minY, maxX - minX, maxY - minY);                //ControlPaint.DrawReversibleFrame(new Rectangle(minX, minY, maxX - minX, maxY - minY),this.BackColor,FrameStyle.Dashed);            }        }        /// <summary>        /// 鼠标松开停止绘图        /// </summary>        /// <param name="sender"></param>        /// <param name="e"></param>        private void data_MouseUp(object sender, MouseEventArgs e)        {            begin = false;        }        /// <summary>        /// 在chart控件上移动鼠标绘图        /// </summary>        /// <param name="sender"></param>        /// <param name="e"></param>        private void chart1_MouseMove(object sender, MouseEventArgs e)        {            if (begin)            {                //重新在chart上面绘图，此处不能用clear方法，clear会清除整个绘图界面chart控件会被清除                this.Refresh();                //获取新的右下角坐标                 secondPoint = new Point(e.X, e.Y);                int minX = Math.Min(firstPoint.X, secondPoint.X);                int minY = Math.Min(firstPoint.Y, secondPoint.Y);                int maxX = Math.Max(firstPoint.X, secondPoint.X);                int maxY = Math.Max(firstPoint.Y, secondPoint.Y);                //画矩形                g2.DrawRectangle(new Pen(Color.Red), minX, minY, maxX - minX, maxY - minY);            }        }        /// <summary>        /// 鼠标松开停止绘图        /// </summary>        /// <param name="sender"></param>        /// <param name="e"></param>        private void chart1_MouseUp(object sender, MouseEventArgs e)        {            begin = false;        }        /// <summary>        /// 在chart控件上按下鼠标        /// </summary>        /// <param name="sender"></param>        /// <param name="e"></param>        private void chart1_MouseDown(object sender, MouseEventArgs e)        {            begin = true;            firstPoint = new Point(e.X, e.Y);        }            }}