生成验证码的例子

using System;
using System.Collections.Generic;
using System.Text;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;

namespace GenerateValiDateCode
{
    class DrawingHelper
    {
        private string CreateCheckCodeString()
        {
            char[] allCharArray =
            {
                '0','1','2','3','4','5','6','7',
                '8','9','A','B','C','D','E','F',
                'G','H','I','J','K','L','M','N',
                'O','P','Q','R','S','T','U','V',
                'W','X','Y','Z' 
            };
            string randomCode = "";
            Random rand = new Random();
            //生成4位验证码字符串
            for (int i = 0; i < 4; i++)
            {
                randomCode += allCharArray[rand.Next(allCharArray.Length)];
            }
            return randomCode;
        }

        public void CreateCheckCodeImage(string filePath)
        {
            //定义图片的宽度
            int width = 55;
            //定义图片的高度
            int height = 22;
            //定义大小为12pt的Arial字体，用于绘制文字
            Font font = new Font("Arial", 12, FontStyle.Bold);
            //定义黑色的单色画笔，用于绘制文字
            SolidBrush brush = new SolidBrush(Color.Black);
            //定义钢笔，用于绘制干扰线
            Pen pen1 = new Pen(Color.Gray, 0);
            Pen pen2 = new Pen(Color.FromArgb(255, 100, 100, 100), 0);
            //创建一个图像
            Bitmap image = new Bitmap(width, height);
            //从图像获取一个绘图面
            Graphics g = Graphics.FromImage(image);
            //清除整个绘图画面并以指定颜色填充
            g.Clear(ColorTranslator.FromHtml("#F0F0F0"));
            //定义文字的绘制矩形区域
            RectangleF rect = new RectangleF(5, 2, width, height);
            //定义一个随机数对象，用于绘制干扰线
            Random rand = new Random();
            //生成两条横向的干扰线
            for (int i = 0; i < 2; i++)
            {
                //定义起点
                Point p1 = new Point(0, rand.Next(height));
                //定义终点
                Point p2 = new Point(width, rand.Next(height));
                //绘制直线
                g.DrawLine(pen1, p1, p2);
            }
            //生成4条纵向的干扰线
            for (int i = 0; i < 4; i++)
            {
                //定义起点
                Point p1 = new Point(rand.Next(width),0);
                //定义终点
                Point p2 = new Point(rand.Next(width),height);
                //绘制直线
                g.DrawLine(pen2, p1, p2);
            }
            //绘制验证码文字
            g.DrawString(CreateCheckCodeString(),font,brush,rect);
            //保存图片为jpeg格式
            image.Save(filePath,ImageFormat.Jpeg);
            //释放对象
            g.Dispose();
            image.Dispose();
        }
    }
}

using System;
using System.Collections.Generic;
using System.Text;

namespace GenerateValiDateCode
{
    class Program
    {
        static void Main(string[] args)
        {
            DrawingHelper dh = new DrawingHelper();
            dh.CreateCheckCodeImage(@"D:\CheckCode.jpg");
        }
    }
}