The question has already been answered. But, here's some added code that will work in ASP.NET WebForms, which enables you to make a local AJAX request to the page w/ the reCaptcha control, then do server-side captcha validation. The page's web method will return true/false.
I got this code from mindfire solutions, but added the execution of JS functions in the Ajax success callback b/c Ajax is making async callbacks.
Javascript:
<script type="text/javascript">
$(function(e) {
$("#submit").click(function() { // my button is type=button, not type=submit
// I'm using jQuery validation and want to make sure page is valid before making Ajax request
if ( $("#aspnetForm").valid() ) {
validateCaptcha(); // or validateCaptchaJson() if you want to use Json
} // end If ($("#aspnetForm").valid())
}); // end $("#submit").click()
}); // end $(function(e)
function validateCaptcha() {
// Individual string variables storing captcha values
var challengeField = $("input#recaptcha_challenge_field").val();
var responseField = $("input#recaptcha_response_field").val();
// Ajax post to page web method that will do server-side captcha validation
$.ajax({
type: "POST",
url: "page.aspx/ValidateCaptcha",
data: "recaptcha_challenge_field=" + challengeField + "&recaptcha_response_field=" + responseField,
async: false
success: function(msg) {
if(msg.d) { // Either true or false, true indicates CAPTCHA is validated successfully.
// this could hide your captcha widget
$("#recaptcha_widget_div").html(" ");
// execute some JS function upon successful captcha validation
goodCaptcha();
} else {
// execute some JS function upon failed captcha validation (like throwing up a modal indicating failed attempt)
badCaptcha();
// don't forget to reload/reset the captcha to try again
Recaptcha.reload();
}
return false;
}
});
}
function validateCaptchaJson() {
// JavaScript object storing captcha values
var captchaInfo = {
challengeValue: Recaptcha.get_challenge(),
responseValue: Recaptcha.get_response()
};
// Ajax post to page web method that will do server-side captcha validation
$.ajax({
type: "POST",
url: "page.aspx/ValidateCaptcha",
data: JSON.stringify(captchaInfo), // requires ref to JSON (http://www.JSON.org/json2.js)
contentType: 'application/json; charset=utf-8',
dataType: 'json',
success: function(msg) {
if(msg.d) { // Either true or false, true indicates CAPTCHA is validated successfully.
// this could hide your captcha widget
$("#recaptcha_widget_div").html(" ");
// execute some JS function upon successful captcha validation
goodCaptcha();
} else {
// execute some JS function upon failed captcha validation (like throwing up a modal indicating failed attempt)
badCaptcha();
// don't forget to reload/reset the captcha to try again
Recaptcha.reload();
}
return false;
}
});
}
</script>
Page's Web Method (VB.NET):
<WebMethod()> _
Public Shared Function ValidateCaptcha(ByVal challengeValue As String, ByVal responseValue As String) As Boolean
' IDEA: Get Private key of the CAPTCHA from Web.config file.
Dim captchaValidtor As New Recaptcha.RecaptchaValidator() With { _
.PrivateKey = "your_private_key_goes_here", _
.RemoteIP = HttpContext.Current.Request.UserHostAddress, _
.Challenge = challengeValue, _
.Response = responseValue _
}
' Send data about captcha validation to reCAPTCHA site.
Dim recaptchaResponse As Recaptcha.RecaptchaResponse = captchaValidtor.Validate()
' Get boolean value about Captcha success / failure.
Return recaptchaResponse.IsValid
End Function
