How to implement reCaptcha "v2" in ASP.NET Core MVC?

Question

I want to add Recaptcha, the second version, not another version, and I want it to be in ASP.NET Core, not MVC, and I searched a lot and did not find the solution.. I hope for help

I have a login controller :

public IActionResult Login([Bind("Username , Password")] User userLogin)
{
    const string id = "id";

    var auth = _context.Users.Where(x => x.Username == userLogin.Username && 
                 x.Password == userLogin.Password).SingleOrDefault();
    var x = _context.Users.Where(x => x.Username == userLogin.Username && x.Password 
                  == userLogin.Password).Select(i => i.UserId).FirstOrDefault();

    if (auth != null)
    {
        // 1 > admin
        // 2 > Accountant
        // 3 > customer
        switch (auth.RoleId)
        {
            case 1: // admin
                HttpContext.Session.SetInt32(id, (int)x);
                return RedirectToAction("Index", "Home");

            case 2:
                HttpContext.Session.SetInt32(id, (int)x);
                return RedirectToAction("AccountantDashboard", "Home");

            case 3:
                HttpContext.Session.SetInt32(id, (int)x);
                return RedirectToAction("Home", "Home");
        }
    }

    return View();
}

and another for view (head and body)

<form asp-action="Login" enctype="multipart/form-data">
    <div class="input-group">
        <label asp-for="Username" class="input--style-2" placeholder="username"></label>
        <input asp-for="Username" class="input--style-2" />
        <span asp-validation-for="Username" class="text-danger"></span>
    </div>

    <div class="input-group">
        <label asp-for="Password" class="input--style-2" placeholder="Password"></label>
        <input asp-for="Password" type="password" class="input--style-2" />
        <span asp-validation-for="Password" class="text-danger"></span>
    </div>

    <div class="p-t-30">
        <button class="btn btn--radius btn--green" type="submit" value="Create">Login</button>
    </div>

    <div style="position: relative ; left: 350px ; bottom: -50px">
        <a class="nav-link text-dark" asp-area="" asp-controller="Home" asp-action="Home">Or back to home page</a>
    </div>
</form>

Answer 1

As far as I know, the reCaptcha "v2" is build based on js and we could directly use it inside the html page.

We could use it like this, firstly put below codes inside your view and it is used to put the g-recaptcha and it contains a callback method, if this method is called that means the user has passed the validation and you could show the button by using JQuery or javascript.

<div class="g-recaptcha" data-callback="recaptcha_callback" data-sitekey="xxxxx"></div> 

Like this:

<script type="text/javascript">
    function recaptcha_callback(){
      $('#login).show();
    }
</script>

More details, you could refer to this article.