Introduction:
Here I will explain how to create captcha in asp.net using c# or create captcha with refresh button in asp.net using c#.
To implement this first we need to new website and design your aspx page like this
<%@ Page
Language="C#"
AutoEventWireup="true"
CodeFile="captcharefresh.aspx.cs"
Inherits="captcharefresh"
%>
<!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>Captcha Image with Refresh Button</title>
<script type="text/javascript">
function RefreshCaptcha() {
var img = document.getElementById("imgCaptcha");
img.src = "Handler.ashx?query="
+ Math.random();
}
</script>
</head>
<body>
<form id="form1" runat="server">
<div>
<img src="Handler.ashx" id="imgCaptcha" />
<a href="#" onclick="javascript:RefreshCaptcha();">Refresh</a>
</div>
</form>
</body>
</html>
After completion of aspx page design need to add one handler file in your website for that Right click on website -à Select Add New Item -à Select Generic Handler file and give name as Handler.ashx and click ok
Now open Handler.ashx file and write the following code
C# Code
<%@ WebHandler
Language="C#"
Class="Handler"
%>
using System;
using System.Web;
using System.Drawing;
using System.Drawing.Imaging;
//using System.Web;
public class Handler : IHttpHandler
{
public void
ProcessRequest(HttpContext context)
{
using (Bitmap b = new Bitmap(150,
40, PixelFormat.Format32bppArgb))
{
using (Graphics g
= Graphics.FromImage(b))
{
Rectangle rect = new Rectangle(0,
0, 149, 39);
g.FillRectangle(Brushes.White, rect);
// Create string to draw.
Random r = new
Random();
int startIndex = r.Next(1, 5);
int length = r.Next(5, 10);
String drawString = Guid.NewGuid().ToString().Replace("-", "0").Substring(startIndex,
length);
// Create font and brush.
Font drawFont = new Font("Arial", 16, FontStyle.Italic
| FontStyle.Strikeout);
using (SolidBrush
drawBrush = new SolidBrush(Color.Black))
{
// Create point for upper-left corner of
drawing.
PointF drawPoint = new PointF(15,
10);
// Draw string to screen.
g.DrawRectangle(new Pen(Color.Red,
0), rect);
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;
}
}
}
Result
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