How to Make Capcha Code in Web Application

Hi ,

Here iam going to make a Capcha Code into our web application before that we have to know that is Capcha Code????

A CAPTCHA or Captcha is a type of challenge-response test used in computing to ensure that the response is not generated by a computer. The process usually involves one computer (a server) asking a user to complete a simple test which the computer is able to generate and grade. Because other computers are unable to solve the CAPTCHA, any user entering a correct solution is presumed to be human. Thus, it is sometimes described as a reverse Turing test, because it is administered by a machine and targeted to a human, in contrast to the standard Turing test that is typically administered by a human and targeted to a machine. A common type of CAPTCHA requires that the user type letters or digits from a distorted image that appears on the screen.

This is a Simple aspx page having a code to create a Cappcha Code

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.Drawing;

using System.Drawing.Text;

using System.Drawing.Imaging;

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

{

protected void Page_Load(object sender, EventArgs e)

{

Bitmap objBMP = new System.Drawing.Bitmap(60, 20); // here we decide the size of capcha image

Graphics objGraphics = System.Drawing.Graphics.FromImage(objBMP);

objGraphics.Clear(Color.Gray);

objGraphics.TextRenderingHint = TextRenderingHint.AntiAlias;

//' Configure font to use for text

Font objFont = new Font("Arial", 8, FontStyle.Bold);

string randomStr = "";

int[] myIntArray = new int[5];

int x;

//That is to create the random # and add it to our string

Random autoRand = new Random();

for (x = 0; x <>

{

myIntArray[x] = System.Convert.ToInt32(autoRand.Next(0, 9));

randomStr += (myIntArray[x].ToString());

}

//This is to add the string to session cookie, to be compared later

Session.Add("randomStr", randomStr);

//' Write out the text

objGraphics.DrawString(randomStr, objFont, Brushes.White, 3, 3);

//' Set the content type and return the image

Response.ContentType = "image/GIF";

objBMP.Save(Response.OutputStream, ImageFormat.Gif);

objFont.Dispose();

objGraphics.Dispose();

objBMP.Dispose();

}

}

*****************************************************************************

After that you simple use this Capcha image into the web page like..

// img alt="" height="30" src="Chapcha.aspx" width="80"

// here we use image and text box to check capcha value

<%-- width="80" />

--%>

//

//

Now the Code on the .cs file on Button Click..

protected void btn_submit_Click(object sender, EventArgs e)

{

try

{

if (Session["randomStr"].ToString().Equals(txt_captcha.Text.Trim()))

{

int log = logic.Loginchk(txt_AccountNo.Text, txt_Password.Text);

if (log == 1)

{

//Logical Part

}

else

{

// Else Part for the logic

}

}

else

{

// lbl_capcha.Text = "Capcha Code is not Matched!!!";

}

}

catch (Exception ex)

{

}

}