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Captcha Images
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With this code sample you can create your own captcha image or captcha control. This resource contains the entire code to help you do so. It contains a normal ASP.NET page "default.aspx" followed by the ASP.NET page that contains the Captcha image. Also, the web.config file for the entire project is given in the examples.
1. default.aspx file follows
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" Debug="true" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
<title>Untitled Page</title>
<style type="text/css">
.correct
{fontfamiy:verdana,arial;fontweight:bold;color:red}
.error
{fontfamiy:verdana,arial;fontweight:bold;color:red}
</style>
</head>
<body onload="Button1_Click">
<form id="form1" runat="server">
<div>
<asp:Image ID="myImage" runat="server" ImageUrl="~/CaptchaControl.aspx" />
<br />
<br />
Enter code: <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<asp:Button ID="Button1" runat="server" Text="Validate" OnClick="Button1_Click" />
<asp:Label ID="MessageLabel" runat="server" Height="50px" Text="" Width="150px"></asp:Label><br /><br />
</div>
</form>
</body>
</html>
2.default.aspx.cs
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;
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
}
}
protected void Button1_Click(object sender, EventArgs e)
{
// validate the code
string userEnteredCode = TextBox1.Text;
ValidateUserCode(userEnteredCode);
}
private void ValidateUserCode(string userEnteredCode)
{
if (Session["Code"].ToString().Equals(userEnteredCode))
{
this.MessageLabel.Text = "Nice to know that you are not a bot.";
this.MessageLabel.CssClass = "correct";
//Response.Write("Nice to know that you are not a bot.");
}
else
{
// clear the session and generate a new code
Session["Code"] = null;
this.TextBox1.Text = "";
this.MessageLabel.CssClass = "error";
this.MessageLabel.Text = "the text u typed is incorrect please try again....";
//Response.Write("the text u typed is incorrect please try again");
}
}
}
3.CaptchaControl.aspx
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="CaptchaControl.aspx.cs" Inherits="CaptchaControl" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Untitled Page</title>
</head>
<body>
<form id="form1" runat="server">
<div>
</div>
</form>
</body>
</html>
4.CaptchaControl.aspx.cs is the code-behind file for CaptchaControl.aspx
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;
using System.Drawing.Imaging;
using System.Text;
public partial class CaptchaControl : System.Web.UI.Page
{
private Random rand = new Random();
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
CreateImage();
}
}
private void CreateImage()
{
string code = GetRandomText();
Bitmap bitmap = new Bitmap(200, 50, System.Drawing.Imaging.PixelFormat.Format32bppArgb);
Graphics g = Graphics.FromImage(bitmap);
Pen pen = new Pen(Color.Yellow);
Rectangle rect = new Rectangle(0, 0, 200, 50);
SolidBrush b = new SolidBrush(Color.Black);
SolidBrush blue = new SolidBrush(Color.Blue);
int counter = 0;
g.DrawRectangle(pen, rect);
g.FillRectangle(b, rect);
for (int i = 0; i < code.Length; i++)
{
g.DrawString(code[i].ToString(), new Font("Verdena", 10 + rand.Next(14, 18)), blue, new PointF(10 + counter, 10));
counter += 20;
}
DrawRandomLines(g);
bitmap.Save(Response.OutputStream, ImageFormat.Gif);
g.Dispose();
bitmap.Dispose();
}
private void DrawRandomLines(Graphics g)
{
SolidBrush green = new SolidBrush(Color.Green);
//for (int i = 0; i < 20; i++)
//{
// g.DrawLines(new Pen(green, 2), GetRandomPoints());
//}
}
private Point[] GetRandomPoints()
{
Point[] points = { new Point(rand.Next(10, 150), rand.Next(10, 150)), new Point(rand.Next(10, 100), rand.Next(10, 100)) };
return points;
}
private string GetRandomText()
{
StringBuilder randomText = new StringBuilder();
if (Session["Code"] == null)
{
string alphabets = "abcdefghijklmnopqrstuvwxyz1234567890";
Random r = new Random();
for (int j = 0; j <= 5; j++)
{
randomText.Append(alphabets[r.Next(alphabets.Length)]);
}
Session["Code"] = randomText.ToString();
}
return Session["Code"] as String;
}
}
5. web.config is give below. It is well commented to help you understand.
<?xml version="1.0"?>
<!--
Note: As an alternative to hand editing this file you can use the
web admin tool to configure settings for your application. Use
the Website->Asp.Net Configuration option in Visual Studio.
A full list of settings and comments can be found in
machine.config.comments usually located in
\Windows\Microsoft.Net\Framework\v2.x\Config
-->
<configuration>
<appSettings/>
<connectionStrings/>
<system.web>
<!--
Set compilation debug="true" to insert debugging
symbols into the compiled page. Because this
affects performance, set this value to true only
during development.
-->
<compilation debug="true"/>
<!--
The <authentication> section enables configuration
of the security authentication mode used by
ASP.NET to identify an incoming user.
-->
<authentication mode="Windows"/>
<!--
The <customErrors> section enables configuration
of what to do if/when an unhandled error occurs
during the execution of a request. Specifically,
it enables developers to configure html error pages
to be displayed in place of a error stack trace.
<customErrors mode="RemoteOnly" defaultRedirect="GenericErrorPage.htm">
<error statusCode="403" redirect="NoAccess.htm" />
<error statusCode="404" redirect="FileNotFound.htm" />
</customErrors>
-->
</system.web>
</configuration>
Fayaz
 Attachments
captcha code (20088-6359-Captcha.zip)
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