C#绘图

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;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        Pen pen = null; //定义一个画笔pen
        Graphics g = null; //定义一个画布
        Point p0, p1; //定义两个坐标点

        private void Form1_Load(object sender, EventArgs e)
        {
            pen = new Pen(Color.Black);
            g = this.CreateGraphics();


        }

        private void button1_Click(object sender, EventArgs e)
        {
            colorDialog1.ShowDialog();
            
            pen.Color = colorDialog1.Color;

        }

        private void Form1_MouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
                p1 = e.Location;
        }

        private void Form1_MouseMove(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                p0 = p1;
                p1 = e.Location;
                g.DrawLine(pen, p0, p1);//实现画线
            }

        }
    }
}