Sample CacheAttribute for ASP.NET Web Api - i'm not saying this is the best way

gistfile1.cs

namespace ProjectName.WebApi.Infrastructure
{
    using System;
    using System.Net;
    using System.Net.Http.Headers;
    using System.Web.Http.Filters;

    public class CacheAttribute : ActionFilterAttribute
    {
        public CacheAttribute()
        {
            this.Days = 30;
        }

        public int Days { get; set; }

        public int Hours { get; set; }

        public int Minutes { get; set; }

        public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext)
        {
            // actionExecutedContext.Result can be null if there was an exception in the controller
            if (actionExecutedContext.Result != null && actionExecutedContext.Result.StatusCode == HttpStatusCode.OK)
            {
                actionExecutedContext.Result.Headers.Vary.Add("Accept");
                actionExecutedContext.Result.Headers.Vary.Add("Accept-Language");
                if (actionExecutedContext.Result.Headers.CacheControl == null)
                {
                    actionExecutedContext.Result.Headers.CacheControl = new CacheControlHeaderValue { Private = true, Public = true};
                }

                var timespan = new TimeSpan(this.Days, this.Hours, this.Minutes, 0);
                actionExecutedContext.Result.Content.Headers.Expires = new DateTimeOffset(DateTime.Now.Add(timespan));
            }

            base.OnActionExecuted(actionExecutedContext);
        }
    }
}

Won't compile. There is no property Result in HttpActionExecutedContext