Google reCAPTCHA using HttpClient in ASP.NET

Introduction

reCAPTCHA is a free service that protects your site from spam and abuse. It uses advanced risk analysis techniques to tell humans and bots apart. With the new API, a significant number of your valid human users will pass the reCAPTCHA challenge without having to solve a CAPTCHA.

Building The Code

Before you start, visit this link https://www.google.com/recaptcha/intro/index.html and click on the Get reCAPTCHA button and follow the steps.

Let's Get started 

Step 1: Create a class or a method in your controller and add the code below.

   

        public async Task<string> GetRecaptcha()

        {

            var response = HttpContext.Current.Request["g-recaptcha-response"];

            const string secretKey = "your secret key";

            var apiConsumer = new ApiConsumer();

            const string url = "https://www.google.com/recaptcha/";

            apiConsumer.BaseUri = new Uri(url);

            apiConsumer.ContentType = ApiConsumer.ApplicationJson;

            apiConsumer.ResourcePath = string.Format("api/siteverify?secret={0}&response={1}", secretKey, response);

            var resp = await apiConsumer.GetAsync();

            if (resp.IsSuccessStatusCode)

            {

                var result = await resp.Content.ReadAsStringAsync();

                return result;

            }

            return null;

        }

Step 2: You can now call this in your MVC controller method:

  var recaptcha = await _utils.GetGoogleRecaptcha();

                    var obj = JObject.Parse(recaptcha);

                    var status = (bool)obj.SelectToken("success");

                    if (status)

                    {

                          //goto dashboard

                    }

                         //recaptcha failed

Note: I used the Netonsoft JObject to parse the server response.

Refer to this url for the Apiconsumer class implementation http://techcerberus.blogspot.com.ng/2017/03/jwt-in-aspnet-web-api-and-mvc.html

Step 3: Adding the View

<script src='https://www.google.com/recaptcha/api.js' type="text/javascript"></script>
   <div class="g-recaptcha" data-sitekey="sike key"> 

  </div> 

The Result: