How to Use the BotDetect CAPTCHA Feature in SharePoint 2013 WebParts (BotDetect v3.0; deprecated)

After you deploy the BotDetect SharePoint CAPTCHA Feature to your SharePoint farm and activate it in a SharePoint web application, it will automatically add all of the necessary configuration to the web application's web.config that are required in order for the BotDetect Captcha control to work in a SharePoint site. This means that after activating the feature you can easily create your own web parts and application pages that utilize BotDetect Captcha protection in that farm.

These are the steps required to create a simple SharePoint 2013 WebPart which displays a Captcha test and checks that user input matches the displayed Captcha code. We will use C#, but please keep in mind that equivalent VB.NET code is very similar.

Set up a SharePoint Web Part Project

  • Start Visual Studio 2012
  • Select File → New → Project
  • From the Project Template Gallery select Visual C# → Office/SharePoint → SharePoint 2013 - Empty Project

  • At the SharePoint Customization Wizard screen, select: Deploy as a farm solution
  • Specify the site that is a part of the web application in which you have activated the BotDetect SharePoint Captcha Feature

  • Right-click your project from the Visual Studio Solution Explorer and select Add → New Item → WebPart
  • Name the new WebPart BotDetectCaptchaWebPart

  • Right click your project from the Visual Studio Solution Explorer and select References → Add reference, then Browse to the BotDetect Captcha installation folder.
  • If you haven’t modified the installation path during setup, the BotDetect assembly will be located at C:\Program Files\Lanapsoft\BotDetect 3 CAPTCHA Component\Asp.Net\v4.0

Note: There is no need to configure the deployment behavior for the BotDetect assembly because it was deployed with the BotDetect SharePoint Captcha Feature.

Modify SharePoint Web Part Code to Display and Validate the CAPTCHA

To add Captcha protection to the WebPart, we will use four controls:

  • a BotDetect.Web.UI.Captcha control
  • a TextBox for the Captcha code user input
  • a Button invoking Captcha validation
  • a Label displaying the Captcha validation result

When the Validate button is clicked and the form is submitted, user input is compared to the code displayed in the Captcha image.

In this simplified example, we just display the Captcha validation result. In a real-world scenario, the protected action (user registration, comment posting, email sending...) would only be performed if the Captcha test was passed.

The above can be achieved by adding the following C# code in the BotDetectCaptchaWebPart.cs file:

using System;
using System.ComponentModel;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using Microsoft.SharePoint;
using Microsoft.SharePoint.WebControls;

using BotDetect;
using BotDetect.Web;
using BotDetect.Web.UI;

namespace BotDetectCaptchaWebPart.BotDetectCaptchaWebPart
    public class BotDetectCaptchaWebPart : WebPart
        protected override void CreateChildControls()

            // create the Captcha control instance
            Captcha captchaControl = new Captcha();
            captchaControl.ID = "BotDetectCaptcha";
            // set Captcha locale; if you don't specify a locale,
            //  "en-US" will be used by default
            //captchaControl.Locale = "fr-CA"
            // create the user input textbox
            TextBox captchaCodeTextBox = new TextBox();
            captchaCodeTextBox.ID = "CaptchaCodeTextBox";

            // create the button
            Button validateButton = new Button();
            validateButton.ID = "ValidateButton";
            validateButton.Text = "Validate";
            validateButton.Click +=
              new EventHandler(validateButton_Click);

            // create the Captcha validation result label
            Label messageLabel = new Label();
            messageLabel.ID = "MessageLabel";

            // add all controls to the WebPart

        protected void validateButton_Click(object sender, EventArgs e)
            // get control references
            Captcha captchaControl = 
            TextBox captchaCodeTextBox = 
            Label messageLabel = 

            // get user input
            string captchaText = 
            // clear user input, since each Captcha code 
            // can only be validated once
            captchaCodeTextBox.Text = null;
            // validate the user input
            if (captchaControl.Validate(captchaText))
                messageLabel.Text = "Success!";
                messageLabel.Text = "Error!";

Build & Deploy the CAPTCHA-protected Web Part to SharePoint

  • Build the WebPart project
  • Right-click your project in Solution Explorer and choose Deploy
  • The built WebPart will be deployed to the SharePoint 2013 server instance

Please Note

The information on this page is out of date and applies to a deprecated version of BotDetect™ CAPTCHA (v3.0).

An up-to-date equivalent page for the latest BotDetect Captcha release (v4) is BotDetect v4 Captcha documentation index.

General information about the major improvements in the current BotDetect release can be found at the What's New in BotDetect v4.0 page.