Note:
First, we need an API key, so head on over to https://www.google.com/recaptcha/admin. To gain access to this page you’ll need to be logged into a Google account. You’ll be asked to register your website, so give it a suitable name, then list domains (for example ashishsrivastava.info) where this particular reCAPTCHA will be used. Subdomains (such as blog.ashishsrivastava.info) are automatically taken into account
Code :
Example 1 :
Create Class
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using Newtonsoft.Json;
/// <summary>
/// Summary description for ReCaptchaClass
/// </summary>
public class ReCaptchaClass
{
public static string Validate(string EncodedResponse)
{
var client = new System.Net.WebClient();
string PrivateKey = "Your KEY";
var GoogleReply = client.DownloadString(string.Format("https://www.google.com/recaptcha/api/siteverify?secret={0}&response={1}", PrivateKey, EncodedResponse));
var captchaResponse = Newtonsoft.Json.JsonConvert.DeserializeObject<ReCaptchaClass>(GoogleReply);
return captchaResponse.Success;
}
[JsonProperty("success")]
public string Success
{
get { return m_Success; }
set { m_Success = value; }
}
private string m_Success;
[JsonProperty("error-codes")]
public List<string> ErrorCodes
{
get { return m_ErrorCodes; }
set { m_ErrorCodes = value; }
}
private List<string> m_ErrorCodes;
}
Using webservice
protected static string ReCaptcha_Key = "Your Key";
protected static string ReCaptcha_Secret = "Your Secret";
[WebMethod]
public string VerifyCaptcha(string response)
{
string url = "https://www.google.com/recaptcha/api/siteverify?secret=" + ReCaptcha_Secret + "&response=" + response;
return (new WebClient()).DownloadString(url);
}
HTML PAGE
JS
<script src="https://www.google.com/recaptcha/api.js?onload=myCallBack&render=explicit" async defer></script>
or
<script src='https://www.google.com/recaptcha/api.js'></script>
<div class="g-recaptcha" data-sitekey="6LfWVw8UAAAAAFioLPix8GJ4dJC83PC6V7Kb26Fd"></div>
Validate using class
string EncodedResponse = Request.Form["g-Recaptcha-Response"];
bool IsCaptchaValid = (ReCaptchaClass.Validate(EncodedResponse) == "true" ? true : false);
if (IsCaptchaValid)
{
}
else
{
/
ScriptManager.RegisterStartupScript(this, this.GetType(), "msg", "javascript:alert('Please verify captcha');", true);
}
Validate using Web Service
using Newtonsoft.Json;
MyService objMyService = new MyService();
string EncodedResponse = Request.Form["g-Recaptcha-Response"];
String json = objMyService.VerifyCaptcha(EncodedResponse);
dynamic stuff = JsonConvert.DeserializeObject(json);
if (stuff.success == "True")
{
}
else
{
ScriptManager.RegisterStartupScript(this, this.GetType(), "msg", "javascript:alert('Please verify captcha');", true);
}
