ASP.net 验证码(C#)

/* Copyright all(c) 2005 ZhongFeng, http://blog.csdn.net/SW515 */

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Drawing.Drawing2D;
using System.Drawing;

 public partial class ValidateCode : System.Web.UI.Page

 {

  private void Page_Load(object sender, System.EventArgs e)

  {

   this.CreateCheckCodeImage(GenerateCheckCode());

  }

  #region Web 窗体设计器生成的代码

  override protected void OnInit(EventArgs e)

  {

   //

   // CODEGEN: 该调用是 ASP.NET Web 窗体设计器所必需的。

   //

   InitializeComponent();

   base.OnInit(e);

  }

  

  /// <summary>

  /// 设计器支持所需的方法 - 不要使用代码编辑器修改

  /// 此方法的内容。

  /// </summary>

  private void InitializeComponent()

  {   

   this.Load += new System.EventHandler(this.Page_Load);

  }

  #endregion

  private string GenerateCheckCode()

  {

   int number;

   char code;

   string checkCode = String.Empty;

   System.Random random = new Random();

   for(int i=0; i<5; i++)

   {

    number = random.Next();

    if(number % 2 == 0)

     code = (char)('0' + (char)(number % 10));

    else

     code = (char)('A' + (char)(number % 26));

    checkCode += code.ToString();

   }

   Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));

   return checkCode;

  }

  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 * 12.5)), 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);

    //画图片的背景噪音线

    for(int i=0; i<25; 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, y1, x2, y2);

    }

    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();

   }

  }

 }

 

　　假如以上验证码生成器页面名为：CheckCode.aspx，那么在登录页面中使用“<IMG>” 这个 HTML 元素来显示生成的验证码图片：<IMG src="CheckCode.aspx">

　　在登录页面的登录按钮的处理事件中使用以下代码判断验证码：

  private void btnLogin_Click(object sender, System.Web.UI.ImageClickEventArgs e)

  {

   if(Request.Cookies["CheckCode"] == null)

   {

    lblMessage.Text = "您的浏览器设置已被禁用 Cookies，您必须设置浏览器允许使用 Cookies 选项后才能使用本系统。";

    lblMessage.Visible = true;

    return;

   }    if(String.Compare(Request.Cookies["CheckCode"].Value, txtCheckCode.Text, true) != 0)

   {

    lblMessage.Text = "验证码错误，请输入正确的验证码。";

    lblMessage.Visible = true;

    return;

   }

        /*****  其他代码  *****/

  }