ASP.NET MVC3 URL parameters resolving to null

Question

For some reason, whenever I try to resolve a URL with arguments in my local installation of ASP.NET MVC3, the arguments basically end up being null in my controller's handling function.

For example, I have

public class HomeController : Controller 
{
    public ActionResult Foo(string bar)
    {
        ViewBag.Message = bar;
        return View();
    }
}

and try to visit http://localhost/myapp/foo/sometext or http://localhost/myapp/home/foo/sometext, bar basically evaluates to null instead of sometext.

I'm fairly confident that my MVC3 install is working properly, as I've managed to run a separate app with a custom routing rule just a few days back. I'm kind of wary that I might have botched up a config flag somewhere or whatever.

Any ideas on what could be wrong here?

gram · Accepted Answer · 2011-07-05 19:49:32Z

8

The default route mapping expects a parameter named id in your action.

routes.MapRoute(
    "Default", // Route name
    "{controller}/{action}/{id}", // URL with parameters
    new { controller = "Home", action = "Index", id = UrlParameter.Optional }
);

If you change your action to this:

public ActionResult Foo(string id)

it should work. You could also try a URL like this if changing the parameter name isn't possible:

http://localhost/myapp/home/foo/?bar=sometext

edited Jul 5, 2011 at 19:49

answered Jul 5, 2011 at 19:41

gram

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3 Comments

Richard Neil Ilagan Over a year ago

Huh. That definitely did the trick, thanks. However I was under the impression that I should be able to write a controller function like public ActionResult foo(string herp, string derp) {} and then automatically get to it via http://localhost/myapp/home/foo/1/2/ or something similar. Does this mean I'll have to author a custom route for every URL pattern I use in terms of number of arguments (and argument names)? That doesn't sound so convenient.

gram Over a year ago

You would not be able to navigate to an action like public ActionResult foo(string herp, string derp) via http://localhost/myapp/home/foo/1/2/ without a custom route. But you would be able to submit a form via an HTTP POST to it without setting up a custom route as long as you have text boxes for herp and derp. In my experience, it hasn't been difficult to come up with a few conventions that satisfy all of my routing needs in a given project, but it depends on your requirements.

Richard Neil Ilagan Over a year ago

Yeah, I guess it's not too hard to actually come up with the routing rules in the long run. It's just a bit of a hard pill to swallow, especially since my MVC experience comes from CakePHP and CodeIgniter. But don't mind me. :D Thanks for the great help!

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