验证码刷新按钮未显示在验证码MVC中

Question

验证码刷新按钮未显示，我想添加图像而不是按钮。

string captchaenable = System.Configuration.ConfigurationManager.AppSettings["CaptchaEnabled"];

if (captchaenable == "True")
{
    @Html.Captcha("Refresh", "<b>Captcha Code:</b>", 5, "Is required field", false)<p>@ViewBag.ErrMessage</p>
}