Captcha Example In Asp.Net C#

In this tutorial i will explain about Captcha,and how to use Captcha Example In Asp.Net C#.We will use Generic Handler to achieve this.

Design:

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

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>Captcha Example In Asp.Net C#</title>
<style type="text/css">
.bdy
{
margin: 0px auto;
width:900px;
font-family:Calibri;
font-size:14px;
padding-top:100px;
}
</style>
<script type="text/javascript">
function Captcha() {
var img = document.getElementById("img");
img.src = "Captcha.ashx?query=" + Math.random();
}
</script>
</head>
<body class="bdy">
<form id="form1" runat="server">

<div style="text-align:center">
<h1>Captcha Example In Asp.Net C#</h1>
<img src="Captcha.ashx" id="img" style="padding-top:40px" />
<a href="#" onclick="javascript:Captcha();"><img src="refresh.png" style="padding-top:-10px" /></a>
</div>
</form>
</body>
</html>

Handler Code:

<%@ WebHandler Language="C#" Class="Captcha" %>

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Web;

public class Captcha : IHttpHandler {
    
public void ProcessRequest (HttpContext context) {
   using (Bitmap b = new Bitmap(70, 25, PixelFormat.Format32bppArgb))
   {
    using (Graphics g = Graphics.FromImage(b))
    {
     Rectangle rect = new Rectangle(0, 0, 70, 25);
     g.FillRectangle(Brushes.White, rect);
     Random r = new Random();
     int startIndex = r.Next(1, 5);
     int length = r.Next(4, 7);
     String drawString = Guid.NewGuid().ToString().Replace("-", "0").Substring(startIndex, length);
     Font drawFont = new Font("Calibri", 14);
     using (SolidBrush drawBrush = new SolidBrush(Color.Black))
     {
         PointF drawPoint = new PointF(0, 0);
         g.DrawString(drawString, drawFont, drawBrush, drawPoint);
     }
     b.Save(context.Response.OutputStream, ImageFormat.Jpeg);
     context.Response.ContentType = "image/jpeg";
     context.Response.End();
     }
    }
   }
 
    public bool IsReusable {
    get {
    return false;
    }
    }
}

6 replies on “Captcha Example In Asp.Net C#”

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