How to Use Captcha in asp.net mvc [closed]

Question

can any one tell me how to use captcha in asp.net mvc? is there any need to download any control for it?

Answer 1

Hoping it's not too late to put my two cents in...

Introducing MvcReCaptcha

I faced this exact same issue when trying to implement CAPTCHA validation on my first ASP.NET MVC site. After discovering many libraries, I found what seemed (and still seems) to be the most straightforward and efficient library: MvcReCaptcha. Since then, I have used this library for all of my ASP.NET MVC sites.

After you implement MvcReCaptcha, it securely generates a CAPTCHA on your view and provides a boolean value of whether the validation was successful to the action.

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Instructions for Use

Here's how to implement it after downloading and referencing the MvcReCaptcha DLL from your project (instructions copied from MvcReCaptcha home page):

Using ReCaptcha with ASP.NET MVC:

It is now extremely easy to setup ReCaptcha on your Asp.Net MVC Website.

Signup for reCaptcha, http://recaptcha.net/whyrecaptcha.html

How to Use:

Step 1: Add your Public and Private key to your web.config file in appsettings section

<appSettings>
  <add key="ReCaptchaPrivateKey" value=" -- PRIVATE_KEY -- " />
  <add key="ReCaptchaPublicKey" value=" -- PUBLIC KEY -- " />
</appSettings>    

Step 2: Add new namespace to your web.config

<namespaces>
  <add namespace="MvcReCaptcha.Helpers"/>
</namespaces>

Step 3: Implement the logic in your view to actually render the Captcha control

<%= Html.GenerateCaptcha() %>

Step 4: Implement the Controller Action that will handle the form submission and Captcha validation

[CaptchaValidator]
[AcceptVerbs( HttpVerbs.Post )]
public ActionResult CreateComment( Int32 id, bool captchaValid )
{
  if (!captchaValid)
  {
      ModelState.AddModelError("_FORM", "You did not type the verification word correctly. Please try again.");
  }
  else
  {
      // If we got this far, something failed, redisplay form
      return View();
  }
}

Good luck!

Answer 2

If you don't fancy writing your own Captcha (who does!) you can use a Captcha library, such as this:

http://www.coderjournal.com/2008/03/aspnet-mvc-captcha/

With a Captcha library, you add the dll to your project and use the Captcha API to display and validate the Captcha image and input.

Display a Captcha:

<label for="captcha">Enter <%= Html.CaptchaImage(50, 180) %> Below</label><br />
<%= Html.TextBox("captcha") %>

And then make sure you add the Captcha attribute to your method:

[CaptchaValidation("captcha")]

Recaptcha is just one option when it comes to Captcha's (in fact, it's the option selected by Stack Overflow!)