title: How to enable button if recaptcha is valid
body: <p>I have controler named <code>AccountController</code> with recaptcha and code like this:</p>
  
  <pre><code>[HttpPost]
          public ActionResult FormSubmit()
          {
  
              var response = Request["g-recaptcha-response"];
              string secretKey = "6Lf_NnQUAAA......";  //Added my secret key that genereted on my re-captcha
              var client = new WebClient();
              var result = client.DownloadString(string.Format("https://google.com/recaptcha/api/siteverify?secret={0}&amp;response{1}", secretKey, response));
              var obj = JObject.Parse(result);
              var status = (bool)obj.SelectToken("success");
              ViewBag.Message = status ? "successs" : "failed";
  
              return View();
          }
  </code></pre>
  
  <p>Also, I have  <code>LogIn.cshtml</code> view with code like this:</p>
  
  <pre><code>&lt;div&gt;
      @using (Html.BeginForm("FormSubmit", "Home", FormMethod.Post))
      {
          &lt;div class="g-recaptcha" data-sitekey="6Lf_NnQUAAA..."&gt;&lt;/div&gt; //ADDED MY SITE KEY
          &lt;input type="submit" name="commit" value="Join IoT Lab!"&gt;  
      }
  &lt;/div&gt;
  &lt;span style="display:inline-block; font-size:20px;margin:20px 0;padding:20px;border:1px solid #D3D3D3"&gt;
      @ViewBag.Message
  &lt;/span&gt;
  &lt;p&gt;
      By clicking "Join IoT Lab", you agree to our &lt;br /&gt;
      &lt;a href="@Url.Action("PrivacyRulesAndGuidelines", "IOTLabProject")"&gt;Terms and conditions&lt;/a&gt; and &lt;a href="@Url.Action("PrivacyRulesAndGuidelines", "IOTLabProject")"&gt;Privacy policy&lt;/a&gt;
  &lt;/p&gt;
  
  &lt;script src='https://www.google.com/recaptcha/api.js' type="text/javascript"&gt;&lt;/script&gt;
  </code></pre>
  
  <p>Currently, captcha using images for validating, so if I check right images captcha will be valid, but also if I just click submit ("Join IoT Lab") without captcha it will still redirect me... </p>
  
  <p><strong>So, how to enable <code>Join IoT Lab!</code> (commit) button after validating the recaptcha? I mean, how to set recaptcha as required field?</strong></p>
  
  <p>I suppose I should use something like <code>ViewBag</code>, but how?</p>