Why is this MVC route not working?

Question

Hi folks,

here are two routes from my global.asax file. I'm trying to go to the second route and I'm getting a default 404 resource not found error.

When i remove the first route (listed in this example), it works.

How can i fix this, please?

Snippet of global.asax code

// GET: /user/PureKrome/Alert/69
routes.MapRoute(
    "User-Alert-Details",
    "user/{displayName}/alert/{alertId}",
    new { controller = "Account", action = "AlertDetails", alertId = 0 });

// GET: /user/PureKrome/Alert/create
routes.MapRoute(
    "User-Alert-Create",
    "user/{displayName}/alert/create",
    new { controller = "Account", action = "AlertCreate" });

Answer 1

Your first route is a "greedy" route and will happily accept "create" as the alertId in the last parameter. It appears that you intend the alertId parameter to be numeric only, so you should add a constraint to tell the route system that that last parameter must be numeric.

See this tutorial.

For example:

// GET: /user/PureKrome/Alert/69
routes.MapRoute(
    "User-Alert-Details",
    "user/{displayName}/alert/{alertId}",
    new { controller = "Account", action = "AlertDetails", alertId = 0 },
    new { alertId = @"\d+" });

// GET: /user/PureKrome/Alert/create
routes.MapRoute(
    "User-Alert-Create",
    "user/{displayName}/alert/create",
    new { controller = "Account", action = "AlertCreate" });

Note, you can also reverse the order of the routes, but even if you do, you should still include a constraint for correctness if you want alertId to always be a number.

Answer 2

You want the routes to be defined the other way round so that the exact match on create comes before the unconstrained match for alertId. That, or you can add a constraint to alertId as stated by Twisty Maze.

This is because the routing works by trying to match the routes from top to bottom. /user/PureKrome/Alert/create matches on the User-Alert-Details route as it thinks create is the value for alertId. By switching them around it will only match the User-Alert-Create route if the 4th segment is explicitly create and it will fall through to User-Alert-Details if it doesn't.

For clarity, they should work this way around:

// GET: /user/PureKrome/Alert/create
routes.MapRoute(
    "User-Alert-Create",
    "user/{displayName}/alert/create",
    new { controller = "Account", action = "AlertCreate" });

// GET: /user/PureKrome/Alert/69
routes.MapRoute(
    "User-Alert-Details",
    "user/{displayName}/alert/{alertId}",
    new { controller = "Account", action = "AlertDetails", alertId = 0 });

Answer 3

If you have another issue like this, try Phil Haack's url debugger at http://haacked.com/archive/2008/03/13/url-routing-debugger.aspx