In this post we will take a look on image code matching functionality which we can see in numerous web sites now days. So what is CAPTCHA? Well, CAPTCHA is technique of showing some random alphanumeric text image to user and verify that the user has entered the same text in the verification box or not.
The term CAPTCHA (for Completely Automated Turing Test To Tell Computers and Humans Apart) came in 2000 and was first developed at CMU for Yahoo.
This is very useful technique to stop abusive comments by bots, spams at a lot of places like any site registration, forums, blogs etc. where bots (automated programes) imitate real user and try to spam your product or any sort of information where you are expecting real users
In order to have your website, page CAPTCHA enabled you can write the code by your self for generating the random images and then doing post validation or you can get already written code from net. You can either use it as a dll from codeplex where you can add this to your toolbox and use it as a Control and then do some modifications related to randomization of images, styles, orientation etc in your web.config. Here is the link for CodePlex captcha code as well as the documentation (http://www.codeplex.com/CAPTCHAGenerator ).
The second way is to get the code from web and use it. Here you can make some modifications too as per your requirement. BUT in both the scenarios take a look at the license and then only use it. You should not fall into any issues later
You can also download CAPTCHA from reCAPTCHA by visiting https://admin.recaptcha.net/accounts/login/?next=/recaptcha/createsite and signing in.
Below is a snapshot of CAPTCHA looks like etc.
Hope this will help you. bye for now.
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