Simple Captcha Using C#

Abstract

This will show you how to create a simple captcha which you can play with to rotate add more effect etc.

I was trying to find a solution to block spammers adding data to our database using C#. This is the quick solution I found.
First create an image tag in the webform that has the submit form.
<IMG height="30" alt="" src="Turing.aspx" width="80">
As you see the source for the picture will be a file called "Turing.aspx".
Later create the webform "Turing.aspx" with the code below

public class Turing1 : System.Web.UI.Page {
private void Page_Load(object sender, System.EventArgs e) {
Bitmap objBMP =new System.Drawing.Bitmap(60,20);
Graphics objGraphics = System.Drawing.Graphics.FromImage(objBMP);
objGraphics.Clear(Color.Green);
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<5;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(); }
}
And this is the code for the submit button on the main form
private void btnSubmit_ServerClick(object sender, System.EventArgs e)
{
if (Page.IsValid && (txtTuring.Value.ToString () ==Session["randomStr"].ToString ()))
{ // The Code to insert data } else
{
Label1.Text ="Please enter info correctly";
} }
4) Finally make sure you add the related System libraries,
using System.Drawing;
using System.Drawing.Text;
using System.Drawing.Imaging;
in front of the class and this is it.
Hope this helps. Regards
http://www.ottawatutors.com


Comments

  • There are no comments yet. Be the first to comment!

Leave a Comment
  • Your email address will not be published. All fields are required.

Top White Papers and Webcasts

  • Java developers know that testing code changes can be a huge pain, and waiting for an application to redeploy after a code fix can take an eternity. Wouldn't it be great if you could see your code changes immediately, fine-tune, debug, explore and deploy code without waiting for ages? In this white paper, find out how that's possible with a Java plugin that drastically changes the way you develop, test and run Java applications. Discover the advantages of this plugin, and the changes you can expect to see …

  • Specialization and efficiency are always in need. Whether it's replacing an aging roof, getting a haircut, or tuning up a car, most seek the assistance of trusted experts. The same is true in the business world, where an increasing number of companies are seeking the help of others to administer their IT systems and services. This special edition of Unleashing IT highlights a new breed of IT caretaker -- Cisco Powered service providers -- and the business advantages and operational efficiencies they …

Most Popular Programming Stories

More for Developers

Latest Developer Headlines

RSS Feeds