How to use recaptcha in ASP.NET
Its a common requirement that we require a captcha to be integrated on our page. I would like to mention a free captcha service which can be implemented in integrated on websites.What is reCaptcha?
- reCAPTCHA is a free CAPTCHA service that helps to digitize books, newspapers and old time radio shows.
- It’s Free! Yep, reCAPTCHA is free.
- It’s Easy. reCAPTCHA is a Web service. As such, adopting it is as simple as adding
a few lines of code on your site. - It’s Accessible. reCAPTCHA has an audio test that allows blind people to freely
navigate your site. - It’s Secure. Most other CAPTCHA implementations can be easily broken.
- It’s Popular. Over 100,000 sites use reCAPTCHA, including household names like Facebook, Ticketmaster, and Craigslist.
- Whenever uses input data in reCaptcha control, they actually help digitizing books.
which are required to integrate it into a ASP.NET page.
Steps to Integrate reCaptcha in ASP.NET
- Register for a reCaptcha key : As a first step we need to register for recaptcha keys. Navigate to Get reCaptcha
URL to signup for the keys. After we register for the keys, we get a
public and private keys which we need to use in our asp.net page. By
default all keys work on localhost as well.
- Download reCaptcha library for ASP.NET: Download the dll file from here. Also add the reference to the dll in the asp.net project.
- Add reCaptcha widget on ASP.NET page : Insert the reCAPTCHA control into the form you wish to protect by adding the following code snippets:
- At the top of the aspx page, insert this:
<%@ registertagprefix="recaptcha" namespace="Recaptcha" assembly="Recaptcha" %> - Then insert the reCAPTCHA control inside of the form tag:
<recaptcha:recaptchacontrolid="recaptcha"runat="server"publickey="your_public_key"privatekey="your_private_key"/>
- At the top of the aspx page, insert this:
- Make sure you use ASP.NET validation to validate your form (you should check Page.IsValid on submission).
Markup:
<%@
Page Language="C#" AutoEventWireup="true"
CodeBehind="RecaptchaPage.aspx.cs"
Inherits="ContosoUniversity.RecaptchaPage" %><%@ Register TagPrefix="recaptcha" Namespace="Recaptcha" Assembly="Recaptcha" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><head runat="server"> <title></title></head><body> <form id="form1" runat="server"> <div> <asp:Label Visible="true" ID="lblResult" runat="server" /> <recaptcha:RecaptchaControl ID="recaptcha" runat="server" Theme="red" PublicKey="6LcoxcASAAAAAGAQQz_xOTk4-ALrRQri_Cf8AuhL" PrivateKey="6LcoxcASAAAAALfZhquqene7_4bTrzmuqHBrkuk0" /> <asp:Button ID="btnSubmit" runat="server" Text="Submit" OnClick="btnSubmit_Click" /> </div> </form></body></html> |
public partial class RecaptchaPage : System.Web.UI.Page{ protected void Page_Load(object sender, EventArgs e) { } protected void btnSubmit_Click(object sender, EventArgs e) { if (Page.IsValid) { lblResult.Text = "Captcha sucessfull!"; lblResult.ForeColor = System.Drawing.Color.Green; } else { lblResult.Text = "Incorrect"; lblResult.ForeColor = System.Drawing.Color.Red; } }} |
When I entered incorrect captcha text and pressed submit button following was the output:
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