Adding reCAPTCHA to ASP.NET MVC

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

• Go to Get reCAPTCHA, which gives you the public and private keys you need to use reCAPTCHA with your site.
• Download the latest .NET library at: http://code.google.com/p/recaptcha/downloads/list. Currently: dotnet-1.0.4.0.
• Add <%= Html.GenerateCaptcha()%> to the form you want to protect with the reCAPTCHA. Naturally, you have to add the namespace for the extension to be recognized, some of the options:
  • Add the namespace to the web.config:
    ASP.NET

    <pages>
          <namespaces>
    ...
            <add namespace="Recaptcha" />

  • Add the namespace at the view:
    ASP.NET

    <%@ Import Namespace="Recaptcha" %>

  • Add your own extension method that wraps it. I changed the signature to return MvcHtmlString to prevent double encoding when using it with “<%:” instead of “<%=”
    C#

    public static MvcHtmlString GenerateCaptcha(this HtmlHelper htmlHelper)
    {
        var html = Recaptcha.RecaptchaControlMvc.GenerateCaptcha(htmlHelper);
        return MvcHtmlString.Create(html);
    }

• Add the RecaptchaControlMvc.CaptchaValidator attribute to your controller. Also add parameters named captchaIsValid and captchaErrorMessage. Just like:
  C#

  [RecaptchaControlMvc.CaptchaValidator]
  public ActionResult MyMethod(Something else, bool captchaValid, 
     string captchaErrorMessage)
  {
  // do something if (!captchaValid)
  }

• Configure your keys. Some options:
  • Add to appsettings in the web.config, with entries named: RecaptchaPublicKey and RecaptchaPrivateKey
  • Set at Application Start:
    C#

    RecaptchaControlMvc.PrivateKey = privKey;
    RecaptchaControlMvc.PublicKey = pubKey;