MVC 4 RedirectToAction看不到自定义标题

Question

If you start a new Web Project, and create a new MVC4 application (with sub-kind as "WebApi", you can paste the below code in (overwriting HomeController.cs) to get the code to work.

I have a MVC4 application (with WebApi).

I am trying to set a custom-header in a MVC controller method and then do a RedirectToAction. The custom-header is not seen in the second mvc-controller-method.

I am able to set a cookie in the first mvc-controller-method and see it in the second mvc-controller-method (after a RedirectToAction).

Is there a way to see the custom-header I set in the second mvc-controller-method after a RedirectToAction ?

Thanks.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Web;
using System.Web.Mvc;
using System.Web.Security;

namespace MyMvc4WebApiProjectNamespace.Controllers
{
    public class HomeController : Controller
    {

        private const string CustomCookieName = "CustomCookieName";
        private const string CustomHeaderName = "X-CustomHeaderName";
        private const string IISExpressRootUrl = "http://localhost:55937/"; /* open up the project properties and go to the web tab and find the iis-express area to get the correct value for your environment */

        public ActionResult Index()
        {

            IEnumerable<string> webApiValues = null;
            string value1 = null;
            string value2 = null;

            HttpClientHandler handler = new HttpClientHandler
            {
                UseDefaultCredentials = true,
                PreAuthenticate = true
            };


            using (var client = new HttpClient(handler))
            {

                string valuesUri = IISExpressRootUrl + "api/Values";

                webApiValues = client
                            .GetAsync(valuesUri)
                            .Result
                            .Content.ReadAsAsync<IEnumerable<string>>().Result;

                if (null != webApiValues)
                {
                    value1 = webApiValues.ElementAt(0);
                    value2 = webApiValues.ElementAt(1);
                }
                else
                {
                    throw new ArgumentOutOfRangeException("WebApi call failed");
                }
            }


            HttpCookie customCookie = new HttpCookie(CustomCookieName, "CustomCookieValue_ThisShowsUpIn_MyHomeControllerAlternateActionResult_Method");
            Response.Cookies.Add(customCookie);

            HttpContext.Response.AppendHeader(CustomHeaderName, "CustomHeaderValue_This_Does_Not_Show_Up_In_MyHomeControllerAlternateActionResult_Method");
            //Response.AppendHeader(CustomHeaderName, value2);

            return RedirectToAction("MyHomeControllerAlternateActionResult");
        }

        public ActionResult MyHomeControllerAlternateActionResult()
        {
            IEnumerable<string> webApiReturnValues = null;


            CookieContainer cookieContainer = new CookieContainer();
            foreach (string cookiename in Request.Cookies)
            {
                if (cookiename.Equals(CustomCookieName, StringComparison.OrdinalIgnoreCase))
                {
                    var cookie = Request.Cookies[cookiename];
                    cookieContainer.Add(new Cookie(cookie.Name, cookie.Value, cookie.Path, "localhost"));
                }
            }

            if (cookieContainer.Count < 1)
            {
                throw new ArgumentOutOfRangeException("CookieContainer did not find the cookie I was looking for");
            }
            else
            {
                Console.WriteLine("This is what actually happens.  It finds the cookie.");
            }

            HttpClientHandler handler = new HttpClientHandler
            {
                UseCookies = true,
                UseDefaultCredentials = true,
                PreAuthenticate = true,
                CookieContainer = cookieContainer
            };


            using (var client = new HttpClient(handler))
            {
                bool customHeaderWasFound = false;
                if (null != this.Request.Headers)
                {
                    if (null != this.Request.Headers[CustomHeaderName])
                    {
                        IEnumerable<string> headerValues = this.Request.Headers.GetValues(CustomHeaderName);
                        client.DefaultRequestHeaders.Add(CustomHeaderName, headerValues);
                        customHeaderWasFound = true;
                    }
                }

                /*I wouldn't expect it to be in the below, but I looked for it just in case */
                if (null != this.Response.Headers)//
                {
                    if (null != this.Response.Headers[CustomHeaderName])
                    {
                        IEnumerable<string> headerValues = this.Response.Headers.GetValues(CustomHeaderName);
                        client.DefaultRequestHeaders.Add(CustomHeaderName, headerValues);
                        customHeaderWasFound = true;
                    }
                }

                if (!customHeaderWasFound)
                {
                    Console.WriteLine("This is what actually happens.  No custom-header found.  :(     ");
                }

                string valuesUri = IISExpressRootUrl + "api/Values";

                webApiReturnValues = client
                            .GetAsync(valuesUri)
                            .Result
                            .Content.ReadAsAsync<IEnumerable<string>>().Result;

                if (null == webApiReturnValues)
                {
                    throw new ArgumentOutOfRangeException("WebApi call failed");
                }

            }

            return View(); /* this will throw a "The view 'MyHomeControllerAlternateActionResult' or its master was not found or no view engine supports the searched locations" error, but that's not the point of this demo. */
        }
    }
}

Answer 1

Response headers are never copied automatically to requests - so setting any custom headers on response will not impact next request issued to handle 302 redirect.

Note that it is the case even with cookies: response comes with "set this cookie" header, and all subsequent request will get "current cookies" header.

If you have your own client you may be able to handle 302 manually (not possible if you are using browser as client).

Answer 2

As another answer stated, response headers are about this response, not the next one. Redirecting is not a server-side action. A redirect instructs the client to perform a completely new request, and of course in a new request, the response headers for the old request are not present. So return RedirectToAction("MyHomeControllerAlternateActionResult"); is guaranteed to not have this response's headers when the browser initiates the new request.

In trying to solve this problem, one might think of trying to persist the data to the next request server-side, such as through a cookie or in an explicit session variable, or implicitly via use of ViewBag/ViewData/TempData. However, I don't recommend this as using session state heavily has performance implications in large/high-usage web sites, plus there are other negative and subtle side-effects that you may run into down the road. For example, if a person has two browser windows open to the same web site, they can't be doing different actions reliably, as the session data for one window can end up being served to the other one. Avoid session usage as much as possible in your web site design—I promise this will benefit you down the road.

A slightly better way, though still with its problems, is to redirect to a URL with querystring parameters containing a payload. And, instead of the whole set of data, you can provide a key that can be pulled from the session (as long as it's also bound to their IP address and is large like a GUID or two together). However, relying on session state is still not ideal as stated before.

Instead, consider using server-side redirection such as child actions. If you find that hard because what you want to call is a main controller you have a few options:

1. If you're using dependency injection, add a parameter to the current controller (saving it from the constructor and using it in the request method) that is the desired controller you want to "redirect" to. You can then call that controller directly. This may not be ideal (as all calls to this controller also have to new up a copy of that one), but it does work. Trying to new up the other controller manually can also work, but for reasons I don't fully remember, I think this can give some additional problems. In any case, this method can give issues accessing the HttpRequest context and other context objects correctly, though this can be worked around.

2. Rearchitect your application so that controllers are not the place where full pages are rendered. Instead, use them as "smart routers" that call child actions to perform the real work. Then, you can call the same child actions from any controller. But this still has problems.

3. Perhaps the best way is to add custom routing logic through action filters or other means (search the web!) so that the correct controller is hit in the first place! This may not always be possible, but sometimes the need to redirect to another controller mid-procedure actually points to a larger design problem. Focusing on how to cause the knowledge of which controller to hit to be available earlier in the pipeline (such as during routing) can reveal architecture problems, and can reveal likely solutions to them.

There may be other options that I haven't thought of, but at least you have a few alternatives to the simple "no way to do that."

Answer 3

I was able to do something similar like what the user is requesting in the following (rudimentary) way:

• In the redirect, add a custom query string parameter
• Create a custom Module that checks for that parameter and appends the custom header (read http://dotnetlionet.blogspot.com/2015/06/how-to-add-httpmodule-in-mvc5.html on how to do your own module) In this way I was able to get my custom headers to be picked up