public static class CaptchaHelper
    {
        public static string Captcha(this HtmlHelper helper, string text)
        {
            string srcPath = System.Web.VirtualPathUtility.ToAbsolute("~/Handler1.ashx");
            string htmlContent = string.Empty;
            htmlContent += "<script type=\"text/javascript\">function __rc(){document.getElementById(\"" + text +
                           "\").src = \"../Handler1.ashx?query=\" + Math.random();}</script>";
            htmlContent += string.Format("<img id=\"{0}\" src=\"{1}\" alt=\"Captcha Image\"/>", text, srcPath);
            htmlContent += "<a href=\"#\" onclick=\"javascript:__rc();\">Reset</a>";
            return htmlContent;
        }
    }

And in the View you can use like, you may need to import the Namespace of CaptchaHelper class.

 < %= Html.Captcha("Sample") %>

It will render a security image. Happy Programming