ReCaptcha with Asp.Net MVC

Saturday, November 13th, 2010 | .net development, .Net Technology, .net web development, .net website development, Asp.Net, asp.net developers, aspdotnetstorefront solutions, b2c web development, dotnetnuke development, ecommerce solution | admin

These are just a few steps, as the latest reCAPTCHA library has all the pieces you need for asp.net MVC:

Step 1 – Create Your ReCAPTCHA Account
Go to the ReCAPTCHA site and sign up for your keys. You will get a private key and and a public key.

Step 2 – Download the .Net Library for ReCAPTCHA
Get reCAPTCHA Library and add this to your ASP.NET MVC project as a reference.
Step 3 – Create Action Filter and handle the Captcha validation

public class CaptchaValidator : ActionFilterAttribute

{
	private const string challenge_field_key = "recaptcha_challenge_field";
        private const string response_field_key = "recaptcha_response_field";

        public override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            var captchaCha_Value = filterContext.HttpContext.Request.Form[challenge_field_key];
            var captchaResp_Value = filterContext.HttpContext.Request.Form[response_field_key];
            var captchaValidtor = new Recaptcha.RecaptchaValidator
                                      {
                                          PrivateKey =  '< Your Private Key>',
                                          RemoteIP = filterContext.HttpContext.Request.UserHostAddress,
                                          Challenge = captchaChallengeValue,
                                          Response = captchaResponseValue
                                      };

            var captchaResponse = captchaValidtor.Validate();
            filterContext.ActionParameters["captchaValid"] = captchaResponse.IsValid;

            base.OnActionExecuting(filterContext);
        }
}

[CaptchaValidator]
[AcceptVerbs( HttpVerbs.Post )]
public ActionResult CreateComment( Int32 id, bool captchaValid )
{
.. ..... ...
}

Step 3 – Create a Html Helper to build and render the Captcha control

public static string GenerateReCaptcha( 'HtmlHelper helper' )
{

	var captchaControl = new Recaptcha.RecaptchaControl
        	{
	                ID = "recaptcha",
                	Theme = "blackglass",
        		PublicKey = --<Your Public Key  > --,
                        PrivateKey = --<Your Private Key > --
		};

	var htmlWriter = new HtmlTextWriter( new StringWriter() );

	captchaControl.RenderControl(htmlWriter);

	return htmlWriter.InnerWriter.ToString();
}

Step 4 Render the Captcha control

<:%= Html.GenerateReCaptcha() %>:

You can get ReCAPTCHA into your site in about 5 minutes, but it might take some time to perfect how you want it to integrate with you current scheme