Download Project  (Full Project)

Step-1

In this part i will show how to use Google Recaptcha Using ASP.NET MVC. First open visual studio then create a new project then select asp.net web application.  Now select Empty then click ok. If you want you can change project name or solution name. Visual studio creates a default project for you.  Now you have to create a controller name as “Captcha” under controller folder. In this controller contain an index method. Now create an Empty view for the index method. Then create a method name as FormSubmit. This method is “HttpPost”. When submit the form then this method is called. This method also takes secret key. Given bellow the controller code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using Newtonsoft;
using System.Net;

namespace GoogleCaptcha1.Controllers
{
    public class CaptchaController : Controller
    {
        //
        // GET: /Captcha/

        public ActionResult Index()
        {
            return View();
        }

        //need to write post here

        [HttpPost]
        public ActionResult FormSubmit()
        {
            //Validate Google recaptcha below

            var response = Request["g-recaptcha-response"];
            string secretKey = "6LffNi4UAAAAAPOmrneA-_KYwXFZmYleNAqJeDsB";
            var client = new WebClient();

            ViewData["Message"] = "Google reCaptcha validation success";


            //Here I am returning to Index view: 

            return View("Index");
        }
    }
}

Step-2

View pass the value into controller then c# controller receive the value and captcha work. In this view pass the value use rezor syntax. Given bellow the view code:

@{
    ViewBag.Title = "Index";
}

<h2>Index</h2>

<div>
    @using (Html.BeginForm("FormSubmit", "Captcha", FormMethod.Post))
{
    <div class="g-recaptcha" data-sitekey="6LffNi4UAAAAAN6-VAiY1ku46Wl9fYlpeYFm2epi"></div>
    <input type="submit" value="Submit" />
}
    
</div>
<span style=" font-size:20px;margin:20px 0;padding:20px;border:1px solid #ff0000">
    @ViewData["Message"]
</span>

<script src='https://www.google.com/recaptcha/api.js' type="text/javascript"></script>

Step-3

Now build and run the project.