Using Google reCAPTCHA in ASP.NET MVC - Invalid reCAPTCHA Label

InvalidGoogleCaptchaLabel.cs

public static class InvalidGoogleCaptchaHelper
{
    public static IHtmlString InvalidGoogleCaptchaLabel(this HtmlHelper helper, string errorText)
    {
        var invalidCaptchaObj = helper.ViewContext.Controller.TempData["InvalidCaptcha"];

        var invalidCaptcha = invalidCaptchaObj?.ToString();
        if (string.IsNullOrWhiteSpace(invalidCaptcha)) return MvcHtmlString.Create("");

        var buttonTag = new TagBuilder("span")
        {
            Attributes =
            {
                new KeyValuePair<string, string>("class", "text text-danger")
            },
            InnerHtml = errorText ?? invalidCaptcha
        };

        return MvcHtmlString.Create(buttonTag.ToString(TagRenderMode.Normal));
    }
}