BuildFeed/Global.asax.cs

using System;
using System.Web;
using System.Web.Mvc;
using System.Web.Optimization;
using System.Web.Routing;

namespace BuildFeed
{
    public class MvcApplication : System.Web.HttpApplication
    {
        protected void Application_Start()
        {
            AreaRegistration.RegisterAllAreas();
            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
            RouteConfig.RegisterRoutes(RouteTable.Routes);
            BundleConfig.RegisterBundles(BundleTable.Bundles);

            DateTimeModelBinder db = new DateTimeModelBinder();

            ModelBinders.Binders.Add(typeof(DateTime), db);
            ModelBinders.Binders.Add(typeof(DateTime?), db);
        }

        public override string GetVaryByCustomString(HttpContext context, string custom)
        {
            switch(custom)
            {
                case "userName":
                    return context.User.Identity.Name.ToLower();
            }

            return "";
        }
    }
}