页面验证码

Posted on 2008-11-24 12:44 MFlower 阅读(276) 评论(1) 收藏举报

代码使用示范：

登陆页面前台代码，假设该页面为：Login.aspx（非正式登陆页面，只用于测试）

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Login.aspx.cs" Inherits="Login" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<title>登陆页面验证码测试</title>

</head>

<body>

<div>

<asp:Image ID="Image1" runat="server" ImageUrl="~/CheckCode.aspx" /><br />

<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>

<asp:Button ID="Button1" runat="server" Text="验证" OnClick="Validate" /><br />

<asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>

</div>

</form>

</body>

</html>

注意到，<asp:Image> 控件的 ImageUrl 属性设置为一个网页：CheckCode.aspx，后面讲解该页面。下面查看登陆页面的后台处理代码

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;

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

{

protected void Page_Load(object sender, EventArgs e)

{

}

protected void Validate(object sender, EventArgs e)

{

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

{

this.Label1.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。";

this.Label1.Visible = true;

return;

}

if (String.Compare(Request.Cookies["CheckCode"].Value, this.TextBox1.Text, true) != 0)

{

this.Label1.Text = "验证码错误，请输入正确的验证码。";

this.Label1.Visible = true;

return;

}

该登陆页面只是简单地提取验证码进行测试。下面重点说一下验证码是如何生成的，验证码是由 CheckCode.aspx 提供，只由后台代码提供：

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.IO;

using System.Drawing;

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

{

protected void Page_Load(object sender, EventArgs e)

{

this.CreateCheckCodeImage(GenerateCheckCode());

}

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();

}

}//End class

如果需要验证码更加朦胧，可把注释中“画图片的背景噪音线”和“画图片的前景噪音点”下面的代码去掉！

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