_CookieConsentMessage.cshtml

<div id="cookie-alert">
    <div class="alert">
        <p><strong>Cookies:</strong> please allow us to use cookies for Facebook Like buttons and Google analytics.</p>
        <form class="btn-group-vertical" action="@Url.Action("NoCookies", "Site", new { ReturnUrl = Request.RawUrl })" method="post" data-async="true" data-target="#cookie-alert" >
            <input type="submit" name="decline" class="btn btn-warning" value="Decline" />
        </form>
        <form class="btn-group-vertical" action="@Url.Action("AllowCookies", "Site", new { ReturnUrl = Request.RawUrl })" method="post">
            <input type="submit" name="allow" class="btn btn-success" value="Allow" />
        </form>
    </div>
</div>

asyncform.js

$('form[data-async=true]').on('submit', function (event) {
    var $form = $(this);
    var $target = $($form.attr('data-target'));

    $.ajax({
        type: $form.attr('method'),
        url: $form.attr('action'),
        data: $form.serialize(),

        success: function (data, status) {
            $target.html(data);
        }
    });

    event.preventDefault();
});

SiteController.cs

using Auction.Web.Utility;
using System.Web.Mvc;

namespace Auction.Web.Controllers
{
    [AllowAnonymous]
    public class SiteController : BaseController
    {
        public ActionResult AllowCookies(string ReturnUrl)
        {
            CookieConsent.SetCookieConsent(Response, true);
            return RedirectToLocal(ReturnUrl);
        }

        public ActionResult NoCookies(string ReturnUrl)
        {
            CookieConsent.SetCookieConsent(Response, false);
            // if we got an ajax submit, just return 200 OK, else redirect back
            if (Request.IsAjaxRequest())
                return new HttpStatusCodeResult(System.Net.HttpStatusCode.OK);
            else
                return RedirectToLocal(ReturnUrl);
        }


        [OutputCache(Duration = 60 * 60 * 24 * 365, Location = System.Web.UI.OutputCacheLocation.Any)]
        public ActionResult FacebookChannel()
        {
            return View();
        }
    }
}