ASP.NET验证码

 public 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  *****/

  }