C# GDI在控件上绘图的方法

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);    }  }}