Invisible ReCaptcha V2
The new Invisible reCAPTCHA isn't validated before the specified button is clicked and once it is clicked; reCAPTCHA does its stuff and the user is flagged as being human or not; if they are human, then the associated JavaScript function is triggered.
Let's start with the development:
Step 1

Open the link mentioned below and click Get recaptcha button, as shown below.
Google Recaptcha Link - Google Recaptcha
Step 2

Create an ASPX page and design your form, as shown below.
Step 3

Add the mentioned CSS given below and JavaScript file to your head tag of the form
  1. <link rel="stylesheet" href="https://www.gstatic.com/recaptcha/api2/r20170329125654/demo__ltr.css" type="text/css" />
  2. <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" type="text/css" />
  3. <script src="https://www.google.com/recaptcha/api.js" async="async" defer="defer"></script>
Step 4

Add the mentioned div given below anywhere between form start and end tag.
  1. <div id="googleRecaptchadiv">
  2. <!-- BEGIN: ReCAPTCHA implementation example. -->
  3. <div id="recaptcha-demo" class="g-recaptcha" data-sitekey="6LeLzA4UAAAAANNRnB8kePzikGgmZ53aWQiruo7O" data-callback="onSuccess" data-bind="recaptcha_demo_submit"></div>
  4. <script>
  5. var onSuccess = function(response) {
  6. debugger;
  7. var errorDivs = document.getElementsByClassName("recaptcha-error");
  8. if (errorDivs.length) {
  9. errorDivs[0].className = "";
  10. }
  11. var errorMsgs = document.getElementsByClassName("recaptcha-error-message");
  12. if (errorMsgs.length) {
  13. errorMsgs[0].parentNode.removeChild(errorMsgs[0]);
  14. }
  15. var clickButton = document.getElementById("<%= Button1.ClientID %>");
  16. clickButton.click();
  17. };
  18. </script>
  19. <!-- Optional noscript fallback. -->
  20. <!-- END: ReCAPTCHA implementation example. -->
  21. </div>
Step 5

Now, run the project and you will able to see captcha when you hit Submit button, as mentioned below.


Step 6

Download the source from the attachment named as Google_Invisible_Recaptcha.zip.