C#生成随机验证码

一个lable，一个pictureBox,一个textBox和一个button;

具体代码

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace 创建验证码
{
    public partial class Form1 : Form
    {
        string yzm;
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            CreateImage(yzm=CreateCode());
            this.Text = "创建验证码    by江南小驴";
        }

        /// <summary>
        /// 产生四位随即验证码
        /// </summary>
        /// <returns></returns>
        private string CreateCode()
        {
            char[] ch=new char[4];
            string str=null;
            int i;
            int number;
            Random random = new Random();
            for (i = 0; i < 4; i++)
            {
                number = random.Next(62);//0~9,a~z,A~Z共62位
                if (number < 10)
                    ch[i] = (char)('0' + (char)number);
                else if (number < 36)
                    ch[i] = (char)('a' + (char)(number-10));
                else ch[i] = (char)('A' + (char)(number-36));
                str += ch[i].ToString();
            }
            return str;
        }

        /// <summary>
        /// 生成随即验证码图形
        /// </summary>
        /// <param name="code"></param>
        private void CreateImage(string code)
        {
            //建立位图文件，设置长宽
            System.Drawing.Bitmap image=new
                System.Drawing.Bitmap((int)Math.Ceiling(code.Length*20.0),30);
            Graphics g = Graphics.FromImage(image);

            try
            {
                int i;
                //生成随即生成器
                Random random = new Random();
                //情况图片背景色
                g.Clear(Color.Gray);
              
                //设置图片上各字符的颜色
                int red, green, blue;
                Color[] color = new Color[4];
                for(i=0;i<4;i++)
                {
                    red = random.Next(256);
                    green = random.Next(256);
                    blue = random.Next(256);
                    color[i]=Color.FromArgb(red,green,blue);
                }

                //生成背景噪音线
                for (i = 0; i < 5; i++)
                {
                    int x1 = random.Next(image.Width);
                    int y1 = random.Next(image.Height);
                    int x2 = random.Next(image.Width);
                    int y2 = random.Next(image.Height);
                    g.DrawLine(new Pen(Color.Purple), x1, y1, x2, y2);
                }

                //将产生的随即数以字体的形式写入画面
                Font font = new System.Drawing.Font("Arial",19,System.Drawing.FontStyle.Bold);
                for (i = 0; i <4; i++)
                {             
                    g.DrawString(code.Substring(i, 1), font, new SolidBrush(color[i]),i*image.Width/4+2, 4,null);

                }

                //生成前背景噪点
                Point[] zdian = new Point[150];
                for (i = 0; i < 150; i++)
                {
                    zdian[i].X = random.Next(image.Width);
                    zdian[i].Y = random.Next(image.Height);
                    image.SetPixel(zdian[i].X, zdian[i].Y, Color.FromArgb(random.Next(256), random.Next(256), random.Next(256)));
                }               

                //画图片的边框
                g.DrawRectangle(new Pen(Color.Green), 0, 0, image.Width-1, image.Height-1 );
                this.pictureBox1.Width = image.Width;
                this.pictureBox1.Height = image.Height;
                this.pictureBox1.BackgroundImage = image;
            }
            catch (SyntaxErrorException ex)
            {
                MessageBox.Show(ex.ToString(),"错误提示",MessageBoxButtons.OKCancel);
            }
        }

        private void pictureBox1_Click(object sender, EventArgs e)
        {
            CreateImage(yzm=CreateCode());
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (textBox1.Text.ToLower() == yzm.ToLower())
            {
               
                MessageBox.Show("小样，眼力挺尖！");
            }
            else
            {
                MessageBox.Show("恭喜，你看错了");
            }
        }
    }
}

效果输出