asp.net does not actually support multiple same-named incoming headers

HomeController.cs

using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Web.Mvc;

namespace HeaderChecking.Controllers
{
    public class HomeController : Controller
    {
        public ActionResult Index()
        {
            // send a request with http client api
            HttpWebRequest r = (HttpWebRequest)WebRequest.Create("http://localhost:45651/Home/About");
            r.Accept = "foo/bar, frap/quad,yadda/*";
            r.Headers.Add("Accept-Ex", "foo/bar, frap/quad");
            r.Headers.Add("Accept-Ex", "yadda/*");
            r.GetResponse();

            // send a request with socket api (only way to *actually* produce multiple headers)
            Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.IP);
            socket.Connect("localhost", 45651);
            var data = Encoding.Default.GetBytes(
@"GET /Home/About HTTP/1.1
Host: localhost
Connection: close
Accept: text/plain, text/html
Accept: application/xml
Accept-Ex: foo/bar, frap/quad
Accept-Ex: yadda/*

");
            socket.Send(data, 0, data.Length, SocketFlags.None);

            // mark the end-of-request-body... we also don't bother to read response...
            socket.Shutdown(SocketShutdown.Send);



            ViewBag.Message = "Welcome to ASP.NET MVC!";

            return View();
        }

        public ActionResult About()
        {
            string allRaw = Request.ServerVariables.Get("ALL_RAW");
            string allHttp = Request.ServerVariables.Get("ALL_HTTP");

            string acceptEx1 = Request.ServerVariables.Get("HTTP_ACCEPT_EX");
            string[] acceptEx2 = Request.ServerVariables.GetValues("HTTP_ACCEPT_EX");
            string acceptEx3 = Request.Headers.Get("Accept-Ex");
            string[] acceptEx4 = Request.Headers.GetValues("Accept-Ex");

            string accept1 = Request.ServerVariables.Get("HTTP_ACCEPT");
            string[] accept2 = Request.ServerVariables.GetValues("HTTP_ACCEPT");
            string accept3 = Request.Headers.Get("Accept");
            string[] accept4 = Request.Headers.GetValues("Accept");

            string[] acceptTypes = Request.AcceptTypes;

            //Trace.Assert(acceptEx1 == "foo/bar, frap/quad,yadda/*");
            //Trace.Assert(acceptEx2.Length == 1);
            //Trace.Assert(acceptEx2[0] == "foo/bar, frap/quad,yadda/*");
            //Trace.Assert(acceptEx3 == "foo/bar, frap/quad,yadda/*");
            //Trace.Assert(acceptEx4.Length == 1);
            //Trace.Assert(acceptEx4[0] == "foo/bar, frap/quad,yadda/*");

            return View();
        }
    }
}