Web API Routing Not Recognising Parameters

Question

I have the following WebAPI controller:

namespace MyApp.WebApi.Controllers
{
    [RoutePrefix("api/listing")]
    public class ListingController : ApiController
    {
        [Route("{firstparam:int?}/{nextparam:int?}")]
        public IEnumerable<ListItem> Get(int firstparam = 100, int nextparam = 12)
        {
             // firstparam is always 100, and nextparam is always 12

However, I've tried specifying the URL:

http://localhost:56004/#/listing?firstparam=2

If I specify the URL like this:

http://localhost:56004/#/listing/2

Then it breaks the routing.

Clearly I'm missing something regarding routing; please could someone point me in the right direction?

Nkosi · Accepted Answer · 2017-01-12 18:44:30Z

You are using multiple optional parameter which don't work well for routeTemplates. Normally the last parameter tends to be the optional parameter.

Documentation: Attribute Routing in ASP.NET Web API 2: Optional URI Parameters and Default Values

FIrst make sure the attribute routing is enabled

public static class WebApiConfig
{
    public static void Register(HttpConfiguration config)
    {
        // Attribute routing.
        config.MapHttpAttributeRoutes();

        // Convention-based routing.
        config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "api/{controller}/{id}",
            defaults: new { id = RouteParameter.Optional }
        );
    }
}

To get what you are after

[RoutePrefix("api/listing")]
public class ListingController : ApiController {

    //GET api/listing
    //GET api/listing?firstparam=x
    //GET api/listing?nextparam=y
    //GET api/listing?firstparam=x&nextparam=y
    [HttpGet]
    [Route("")]
    public IEnumerable<ListItem> Get(int firstparam = 100, int nextparam = 12) { ... }
}

The problem with having multiple inline parameters that are optional is that the router wont know which to use which is why they tend to be at the end of the url.

However to get them inline like how you mentioned in your example you are going to need multiple routes.

[RoutePrefix("api/listing")]
public class ListingController : ApiController {

    //GET api/listing
    [HttpGet]
    [Route("")]
    public IEnumerable<ListItem> Get() { return Get(100, 12);  }

    //GET api/listing/2
    //GET api/listing/2/5
    [HttpGet]
    [Route("{firstparam:int}/{nextparam:int?}")]
    public IEnumerable<ListItem> Get(int firstparam, int nextparam = 12) { ... }
}

Alexander Staroselsky · Accepted Answer · 2017-01-12 18:07:48Z

0

You could try using [FromUri] attribute within the params of the Get() method to extract any query params being passed into the "/listing" uri along with a class that consists of int properties firstparam and secondparam.

namespace MyApp.WebApi.Controllers
{
    [RoutePrefix("api/listing")]
    public class ListingController : ApiController
    {
        [Route("")]
        [HttpGet]
        public IEnumerable<ListItem> Get([FromUri] ClassRepresentingParams params)
        {

Hopefully that helps.

edited Jan 12, 2017 at 18:07

answered Jan 12, 2017 at 17:38

Alexander Staroselsky

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5 Comments

Paul Michaels Over a year ago

What would the URL for that look like? It just seems to break the routing (that is, it doesn't find Get)

Alexander Staroselsky Over a year ago

Try adding an [HttpGet] attribute to the method as well. I've updated my answer.

Paul Michaels Over a year ago

HttpGet("") doesn't compile. Without the quotes it makes no difference, I still lose the routing

abdul Over a year ago

it's [HttpGet] only.

Alexander Staroselsky Over a year ago

The configuration for the project may not be set up correctly for attribute based routing. This may be preventing routes from compiling. Within your WebApiConfig class you'd need config.MapHttpAttributeRoutes(); within the Register() method.

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