ASP.NET 验证码源码

验证码效果代码：

/*编写者:吴蒋
  时间:2010-07-21
  修改者:
  修改内容:
 */

using System;
using System.Drawing;
using System.Text;

public partial class Inc_ValidateCode : System.Web.UI.Page
{
    #region 页面事件
    /// <summary>
    /// 页面加载事件
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    protected void Page_Load(object sender, EventArgs e)
    {
        this.CreateCheckCodeImage(GenerateCheckCode());
    }
    #endregion

    #region 函数
    /// <summary>
    /// 随机字母和数字生成函数
    /// </summary>
    /// <returns>string</returns>
    private string GenerateCheckCode()
    {
        int number;//存储随机数
        char code;//字符容器
        StringBuilder checkCode = new StringBuilder();//拼接字符串容器
        Random random = new Random();//创建随机方法对象

        for (int i = 0; i < 5; i++)//循环6次
        {
            number = random.Next();//获得随机数
            if (number % 2 == 0)//偶数
            {
                code = (char)('0' + (char)(number % 10));//获得显示的字符
            }
            else
            {
                code = (char)('A' + (char)(number % 26));//获得显示的字符
            }

            checkCode.Append(code.ToString());//拼接字符串
        }

        Session["CheckCode"] = checkCode;//写入Session
        Session.Timeout = 30;//过期时间
        //Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));       //写入Cookies

        return checkCode.ToString();//返回字符串
    }

    /// <summary>
    /// 创建显示图片
    /// </summary>
    /// <param name="checkCode">要生成的字符串</param>
    private void CreateCheckCodeImage(string checkCode)
    {
        if (checkCode == null || checkCode.Trim() == String.Empty)//如果参数为空直接退出函数
            return;

        System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 22);//生成位图
        Graphics g = Graphics.FromImage(image);//画位图

        try
        {
            Random random = new Random(); //生成随机生成器
            g.Clear(Color.White); //清空图片背景色
            for (int i = 0; i < 25; i++) //画图片的背景噪音线
            {
                int x1 = random.Next(image.Width);//更具图片宽度产生随机数
                int x2 = random.Next(image.Width);//更具图片宽度产生随机数
                int y1 = random.Next(image.Height);//更具图片高度产生随机数
                int y2 = random.Next(image.Height);//更具图片高度产生随机数

                g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);//绘制线
            }

            Font font = new System.Drawing.Font("Arial", 12, (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.DarkRed, 1.2f, true);
            g.DrawString(checkCode, font, brush, 2, 2);

            //画图片的前景噪音点
            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()));
            }

            //画图片的边框线
            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();
        }
    }
    #endregion
}