生成验证码

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Drawing;
using System.Text;
using System.IO;

public partial class VerfiCodeImage : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        this.CreateCheckCodeImage(GenerateCheckCode());
       
    }
    //产生随机验证码     private string GenerateCheckCode()
    {
        int number;
        char code;
        //checkCode装载验证码的载体
        string checkCode = string.Empty;
        //产生单个随机数         System.Random random = new Random();
        //获取4位验证码
        for (int i = 0; i < 4; i++)
        {
            number = random.Next();
            //if (number % 2 == 0)
            //{
                code = (char)('0' + (char)(number % 10));
            //}
            //else
            //    code = (char)('a' + (char)(number % 26));
            checkCode += code.ToString();
        }
        //将获得的校验码存储到Session中         Session["CheckCode"] = checkCode;
        return checkCode;
    }
    //产生验证码图像     private void CreateCheckCodeImage(string checkCode)
    {
        if (checkCode == null || checkCode.Trim() == string.Empty)
            return;
        System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 13.5)), 22);
        Graphics g = Graphics.FromImage(image);
        try
        {
            //生成随机生成器             Random random = new Random();
            //清空图片背景色             g.Clear(Color.White);
            //图片的背景噪音线
            for (int i = 0; i <5; i++)
            {
                int x1 = random.Next(image.Width);
                int x2 = random.Next(image.Width);
                int y1 = random.Next(image.Height);
                int y2 = random.Next(image.Height);
                g.DrawLine(new Pen(Color.Silver), x1, x2, y1, y2);
            }
            Font font = new System.Drawing.Font("Arial", 14, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
            System.Drawing.Drawing2D.LinearGradientBrush brush = new
                    System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue,
                    Color.DarkOrange, 2.2f, true);
            g.DrawString(checkCode, font, brush, 2, 2);
            //图片前景噪音点             //for (int i = 0; i < 100; i++)
            //{
            //    int x = random.Next(image.Width);
            //    int y = random.Next(image.Height);
            //    image.SetPixel(x, y, Color.FromArgb(random.Next()));
            //}
            //图片的边框线
            g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
            System.IO.MemoryStream ms = new System.IO.MemoryStream();
            image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
            Response.ClearContent();
            Response.ContentType = "image/Gif";
            Response.BinaryWrite(ms.ToArray());
        }
        finally
        {
            g.Dispose();
            image.Dispose();
        }
    }
}