How to implement captcha in asp.net mvc?

In this article, I will show how to create captcha in asp.net mvc. A captcha is a validation Layer is used to recognize the type of user before sending data to the server side. It helps to avoid the spam messages or users.

Step 1: To begin install captcha in the project by running the following command in the nuget package manager console.

PM> Install-Package CaptchaMvc.Mvc4

Step 2: Right click on the model folder and create a class and name it as feedback. Copy and paste the following code.

public class FeedBack
    {
        public int Id { get; set; }
        public string Title { get; set; }
        public string Comment { get; set; }
    }

Step 3: Create an asp.net mvc project and right click on the controller folder and create a new controller and name it as RegisterController. Inside the RegisterController copy and paste the following code.

public ActionResult Index()
        {
            return View();
        }
        [HttpPost]
        public ActionResult Index(string empty)
        {
            // Codefor validating the CAPTCHA 
            if (this.IsCaptchaValid("Captchais not valid"))
            {
 
                return RedirectToAction("ThankYouPage");
            }
 
            ViewBag.ErrMessage = "Error: captcha is not valid.";
            return View();
        }
 
        public ActionResult ThankYouPage()
        {
            return View();
        }

Step 4: Right click on the index method and create a view named as index. Copy and paste the following code.

@using CaptchaMvc.HtmlHelpers
@using CaptchaMvc;
@model MymvcApp.Models.FeedBack
@using (Html.BeginForm())
{ 
    @Html.ValidationSummary(true) 
    <br />
    <br />
    <fieldset style="width: 50%; margin: 0 auto;">
        <legend>Register</legend>
        <div>
            <div class="editor-label">
                @Html.LabelFor(model => model.Title)
            </div>
            <div class="editor-field">
                @Html.EditorFor(model => model.Title)
                @Html.ValidationMessageFor(model => model.Title)
            </div>
        </div>
        <div>
            <div class="editor-label">
                @Html.LabelFor(model => model.Comment)
            </div>
            <div class="editor-field">
                @Html.TextAreaFor(model => model.Comment, 5, 40, null)
                @Html.ValidationMessageFor(model => model.Comment)
            </div>
 
        </div>
 
        @Html.MathCaptcha()
 
        <br />
        <p class="Error">@ViewBag.ErrMessage </p>
        <p style="text-align: right; padding-right: 20px;">
            <input type="submit" value="Send" />
        </p>
    </fieldset> 
}

Step 4: Right click on the ThankYouPage method and create a view named as Thankyoupage. Copy and paste the following code.

@{
    ViewBag.Title = "ThankYouPage";
}
 
<h2>ThankYouPage</h2>
 
<b>Thank you sending your valuable feedback to us.</b>

Description: Here I have implemented HTML helper class @Html.MathCaptch(), it will generate mathematical captcha. If you want to implement character captcha then @Html.captcha(4), it will generate 4 character length. When the user enters the correct input, it then verified then it will redirect the user to the thankyoupage

Captcha asp.net c# example: