Issue in MVC routing when GETing integer parameter

Question

I'm at a loss for why this routing issue is occurring.

Route in Global.asax.cs file:

routes.MapRoute(
    "Archives", //Route name
    "{controller}/{action}/{month}", // URL with parameters
    new { controller = "Articles", action = "Archives" },
    new { month = @"^\d+" } // Parameter.defaults
);

Controller:

public ActionResult Archives(int month)
{
    ViewData["month"] = month;
    return View(article);
}

Which keeps throwing the error:

The parameters dictionary contains a null entry for parameter 'month' of non-nullable type 'System.Int32' for method 'System.Web.Mvc.ActionResult Archives(Int32)' in 'AppleWeb.Controllers.ArticlesController'. An optional parameter must be a reference type, a nullable type, or be declared as an optional parameter. Parameter name: parameters

Which is bogus because the URL is: http://localhost:64529/Articles/Archives/12

EDIT- Full routing for all to see:

public static void RegisterRoutes(RouteCollection routes)
{
    routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
    //routes.IgnoreRoute("tellerSurvey.htm/{*pathInfo}");routes.MapRoute(
        "Default", // Route name
        "{controller}/{action}/{id}", // URL with parameters
        new { controller = "Appleweb", action = "Index", id = UrlParameter.Optional } // Parameter defaults
    );

    routes.MapRoute(
        "Contact", //Route name
        "{controller}/{action}/{page}", //URL with parameters
        new { controller = "Appleweb", action = "Contact", page = UrlParameter.Optional } // Paramter defaults
    );

    routes.MapRoute(
        "FormDetails", //Route name
        "{controller}/{action}/{formid}", // URL with parameters
        new { controller = "Resources", action = "FormDetails", formid = 0}
    );

    routes.MapRoute(
        "_calc",
        "{controller}/{action}/{calcid}", // URL with parameters
        new { controller = "Resources", action = "Calc", calcid = UrlParameter.Optional } // Parameter defaults
    );

    routes.MapRoute(
        "Article", //Route name
        "{controller}/{action}/{articleid}", // URL with parameters
        new { controller = "Articles", action = "Article", id = 0 } // Parameter.defaults
    );}

This is an MVC 3 project, so no routingconfig.cs.

Paste full list of your routings especially those that are declared before this one. — Rafal
– Rafal, Commented Feb 3, 2014 at 16:15

LostInComputer · Accepted Answer · 2014-02-03 19:07:45Z

2

Here is the problem: The URL http://localhost:64529/Articles/Archives/12 matches the other routes. It will match the Default, Contact, etc routes.

Edit Simplest solution

    routes.IgnoreRoute("{resource}.axd/{*pathInfo}");

    routes.MapRoute(
        "Archives",
        "{controller}/{action}/{month}",
        new { controller = "Articles", action = "Archives" },
        new { month = @"\d+"}
    );

    //short-circuit for all URLs where the month is not numeric
    //Warning: the 404 will not be handled in <customErrors>
    //Its handled in <httpErrors>
    routes.IgnoreRoute("Articles/Archives/{month}");

    //place all other routes here

Other possibilities

1) replace {controller} with the hard-coded controller name so that /Articles won't match the route. Sample:

    routes.MapRoute(
        "Contact",
        "Appleweb/{action}/{page}",
        new { controller = "Appleweb", action = "Contact", page = UrlParameter.Optional }
    );

Only match URLs that start with /Appleweb

2) use constraint

    routes.MapRoute(
        "Archives", //Route name
        "Appleweb/{action}/{page}",
        new { controller = "Appleweb", action = "Contact", page = UrlParameter.Optional },
        new { controller = "^(?!articles$).*$" } //don't match articles
    );

or

    routes.MapRoute(
        "Archives", //Route name
        "Appleweb/{action}/{page}",
        new { controller = "Appleweb", action = "Contact", page = UrlParameter.Optional },
        new { controller = "appleweb|resources" } //only allow appleweb and resources
    );

3) make the URL of archive unique like http://XXXX/Archives/12

   routes.MapRoute(
        "Archives",
        "Archives/{month}",
        new { controller = "Articles", action = "Archives" },
        new { month = @"\d+" }
   );

edited Feb 3, 2014 at 19:07

answered Feb 3, 2014 at 16:42

LostInComputer

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6 Comments

techmaniac Over a year ago

My understanding of routing was you set the parameters (second line) {controller}, /{action}/{parameter} and you fill in the blanks with what you want articles, archives, month. But what you are writing is that the first line sets it up and should be hard coded as such. So following that logic, I created this: ' routes.MapRoute( "Archives", //Route name "Articles/Archives/{month}", // URL with parameters new { controller = "Articles", action = "Archives" }, new { month = @"^\d+" } // Parameter.defaults );'

LostInComputer Over a year ago

The third parameter is the default values when none is specified. Example: For this route {controller}/{action}, the following URLs resolve to the same controller actions '/Appleweb/Index', '/Appleweb' (index is the default action), '/' (appleweb is the default controller and index is the default action)

techmaniac Over a year ago

So it is working with Articles/Archives/{month} in the URL. I guess don't gut what the Controller parameter is all about then, if you are hard coding.

LostInComputer Over a year ago

The hard code in the first solution is so that only URLs that start with Appleweb matches. We normally don't hard-code.

LostInComputer Over a year ago

I edited my answer. I think the first solution was confusing you.

|

Indi · Accepted Answer · 2014-02-03 16:26:40Z

2

Your route has not given a default value for the month and the action method has a non nullable parameter (int month).

Change your route map to:

 routes.MapRoute(
       "Archives",
       "{controller}/{action}/{month}",
       new { controller = "Articles", action = "Archives", 
                       month = UrlParameter.Optional }
   );

Or action method to accept nullable int for the month parameter:

public ActionResult Archives(int? month) //nullable int
{
    ViewData["month"] = month;
    return View(article);
}

answered Feb 3, 2014 at 16:26

Indi

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5 Comments

Aniket Inge Over a year ago

you were faster than me

techmaniac Over a year ago

The thing is, it isn't (or shouldn't) be an optional parameter. I can't determine what months' articles to display. I also don't understand why it throws an error when there is clearly a parameter that matches the criteria. Not to mention, how does the UrlParameter.Optional mesh with my reg expression for a integer?

Indi Over a year ago

If it isn't an optional parameter, you could assign a default value (say, 1) and make Archives(int month) (i.e. non nullable)

techmaniac Over a year ago

Same as previous, how does that code look with the regular expression code @"^d+"?

Indi Over a year ago

Try month = "0*[0-9][0-9]*" in the same route value dictionary.

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