How to simulate Server.Transfer in ASP.NET MVC?

Question

In ASP.NET MVC you can return a redirect ActionResult quite easily :

 return RedirectToAction("Index");

 or

 return RedirectToRoute(new { controller = "home", version = Math.Random() * 10 });

This will actually give an HTTP redirect, which is normally fine. However, when using google analytics this causes big issues because the original referer is lost so google doesnt know where you came from. This loses useful information such as any search engine terms.

As a side note, this method has the advantage of removing any parameters that may have come from campaigns but still allows me to capture them server side. Leaving them in the query string leads to people bookmarking or twitter or blog a link that they shouldn't. I've seen this several times where people have twittered links to our site containing campaign IDs.

Anyway, I am writing a 'gateway' controller for all incoming visits to the site which i may redirect to different places or alternative versions.

For now I care more about Google for now (than accidental bookmarking), and I want to be able to send someone who visits / to the page that they would get if they went to /home/7, which is version 7 of a homepage.

Like I said before If I do this I lose the ability for google to analyse the referer :

 return RedirectToAction(new { controller = "home", version = 7 });

What i really want is a

 return ServerTransferAction(new { controller = "home", version = 7 });

which will get me that view without a client side redirect. I don't think such a thing exists though.

Currently the best thing I can come up with is to duplicate the whole controller logic for HomeController.Index(..) in my GatewayController.Index Action. This means I had to move 'Views/Home' into 'Shared' so it was accessible. There must be a better way??..

Answer 1

Doesn't routing just take care of this scenario for you? i.e. for the scenario described above, you could just create a route handler that implemented this logic.

Answer 2

Couldn't you just create an instance of the controller you would like to redirect to, invoke the action method you want, then return the result of that? Something like:

 HomeController controller = new HomeController();
 return controller.Index();

Answer 3

Just instance the other controller and execute it's action method.

Answer 4

You could new up the other controller and invoke the action method returning the result. This will require you to place your view into the shared folder however.

I'm not sure if this is what you meant by duplicate but:

return new HomeController().Index();

Edit

Another option might be to create your own ControllerFactory, this way you can determine which controller to create.

Answer 5

Implementing your own dynamic routing by implementing the IRouteHandler might be a solution. See http://stackoverflow.com/questions/379558/mvc-net-routing/379823#379823 for more details.

Answer 6

I found out recently that ASP.NET MVC doesn't support Server.Transfer() so I've created a stub method (inspired by Default.aspx.cs).

    private void Transfer(string url)
    {
        // Create URI builder
        var uriBuilder = new UriBuilder(Request.Url.Scheme, Request.Url.Host, Request.Url.Port, Request.ApplicationPath);
        // Add destination URI
        uriBuilder.Path += url;
        // Because UriBuilder escapes URI decode before passing as an argument
        string path = Server.UrlDecode(uriBuilder.Uri.PathAndQuery);
        // Rewrite path
        HttpContext.Current.RewritePath(path, false);
        IHttpHandler httpHandler = new MvcHttpHandler();
        // Process request
        httpHandler.ProcessRequest(HttpContext.Current);
    }

Answer 7

How about a TransferResult class? (based on Stans answer)

/// <summary>
/// Transfers execution to the supplied url.
/// </summary>
public class TransferResult : RedirectResult
{
    public TransferResult(string url)
        : base(url)
    {
    }

    public override void ExecuteResult(ControllerContext context)
    {
        var httpContext = HttpContext.Current;

        httpContext.RewritePath(Url, false);

        IHttpHandler httpHandler = new MvcHttpHandler();
        httpHandler.ProcessRequest(HttpContext.Current);
    }
}

Answer 8

Here's my modification based upon Markus's modifed version of Stan's original post. I added an additional constructor to take a Route Value dictionary - and renamed it MVCTransferResult to avoid confusion that it might just be a redirect.

I can now do the following for a redirect:

return new MVCTransferResult(new {controller = "home", action = "something" });

My modified class :

public class MVCTransferResult : RedirectResult
{
    public MVCTransferResult(string url)
        : base(url)
    {
    }

    public MVCTransferResult(object routeValues):base(GetRouteURL(routeValues))
    {
    }

    private static string GetRouteURL(object routeValues)
    {
        UrlHelper url = new UrlHelper(new RequestContext(new HttpContextWrapper(HttpContext.Current), new RouteData()), RouteTable.Routes);
        return url.RouteUrl(routeValues);
    }

    public override void ExecuteResult(ControllerContext context)
    {
        var httpContext = HttpContext.Current;

        httpContext.RewritePath(Url, false);

        IHttpHandler httpHandler = new MvcHttpHandler();
        httpHandler.ProcessRequest(HttpContext.Current);
    }
}

Answer 9

I wanted to re-route the current request to another controller/action, while keeping the execution path exactly the same as if that second controller/action was requested. In my case, Server.Request wouldn't work because I wanted to add more data. This is actually equivalent the current handler executing another HTTP GET/POST, then streaming the results to the client. I'm sure there will be better ways to achieve this, but here's what works for me:

RouteData routeData = new RouteData();
routeData.Values.Add("controller", "Public");
routeData.Values.Add("action", "ErrorInternal");
routeData.Values.Add("Exception", filterContext.Exception);

var context = new HttpContextWrapper(System.Web.HttpContext.Current);
var request = new RequestContext(context, routeData);

IController controller = ControllerBuilder.Current.GetControllerFactory().CreateController(filterContext.RequestContext, "Public");
controller.Execute(request);

Your guess is right: I put this code in

public class RedirectOnErrorAttribute : ActionFilterAttribute, IExceptionFilter

and I'm using it to display errors to developers, while it'll be using a regular redirect in production. Note that I didn't want to use ASP.NET session, database, or some other ways to pass exception data between requests.

Answer 10

Not an answer per se, but clearly the requirement would be not only for the actual navigation to "do" the equivalent functionality of Webforms Server.Transfer(), but also for all of this to be fully supported within unit testing.

Therefore the ServerTransferResult should "look" like a RedirectToRouteResult, and be as similar as possible in terms of the class hierarchy.

I'm thinking of doing this by looking at Reflector, and doing whatever RedirectToRouteResult class and also the various Controller base class methods do, and then "adding" the latter to the Controller via extension methods. Maybe these could be static methods within the same class, for ease/laziness of downloading?

If I get round to doing this I'll post it up, otherwise maybe somebody else might beat me to it!

Answer 11

You can use Server.TransferRequest on IIS7+ instead.