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  • Your email address will not be published.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

  • Complex hybrid environments can make it difficult to track interdependencies, increasing the risk of disrupting critical business services. In this white paper by EMA, you'll learn how application discovery and dependency mapping can help you: Meet granular targets for availability, cost, and time-to-revenue for cloud services. Accelerate mean time to repair (MTTR) while communicating better with stakeholders. Manage even the most complex hybrid environments more efficiently and effectively Understand the …

  • When individual departments procure cloud service for their own use, they usually don't consider the hazardous organization-wide implications. Read this paper to learn best practices for setting up an internal, IT-based cloud brokerage function that service the entire organization. Find out how this approach enables you to retain top-down visibility and control of network security and manage the impact of cloud traffic on your WAN.

Most Popular Programming Stories

More for Developers

RSS Feeds

Thanks for your registration, follow us on our social networks to keep up-to-date