404 Errors for WebAPI - Registering routes in HttpModule not working

Question

I am trying to add WebAPI endpoints to an existing forms application but I am getting 404 errors.

I cannot use the Global.asax Application_Start() to register the api routes as suggested by Microsoft here because the current application already has a compiled customization of the Global class which inherits from HttpApplication and they did not mark any of the methods as virtual. doh!

I am trying to load the routes using an HttpModule. I am getting 404 errors for the following URL: https://example.com/webapplication/myapi/Authorize/User

Module code:

using System;
using System.Web;
using System.Web.Http;

public class MyHttpModule : IHttpModule
{
    private static bool HasAppStarted = false;
    private readonly static object _syncObject = new object();

    public void Init(HttpApplication context)
    {
        //https://stackoverflow.com/a/2416546/579148
        if (!HasAppStarted)
        {
            lock (_syncObject)
            {
                if (!HasAppStarted)
                {
                    GlobalConfiguration.Configure(config => RegisterRoutes.Load(config));
                    HasAppStarted = true;
                }
            }
        }
    }

    #region IDisposable Implementation
    #endregion
}

My registration class is in a standalone library:

using System.Web.Http;

public static class RegisterRoutes
{
    public static void Load(HttpConfiguration config)
    {
        config.MapHttpAttributeRoutes();
        config.Routes.MapHttpRoute("DefaultApi", "myapi/{controller}");
    }
}

And my controller:

using System;
using System.Web.Http;
using MyLibrary.Models;

[Route("myapi/[controller]/[action]")]
public class AuthorizeController : ApiController
{
    [HttpGet, ActionName("User")]
    [AllowAnonymous]
    public WebUser GetUser()
    {
        WebUser user = new WebUser();
        user.Key = Guid.Empty.ToString();
        return user;
    }
}

And finally the web.config:

<configuration>
  <!--...-->
  <system.webServer>
    <!--...-->
    <modules>
      <add name="MyModule" type="MyLibrary.MyHttpModule" />
    </modules>
    <!--...-->
  </system.webServer>
  <!--...-->
<configuration>

The webapplication is its own IIS application (its own Global.asax and web.config). I am on Windows 10, CLR version v4.0, and Managed Pipeline is Integrated.

I've tried several other options described here, here, and here but have not had anything but 404s.

TIA!

You are mixing up frameworks. `[Route("myapi/[controller]/[action]")]` is for [tag:asp.net-core] while your code appears to be for [tag:asp.net-web-api] — Nkosi, Aug 17 '18 at 15:45

score 1 · Answer 1 · answered Aug 17 '18 at 15:55

1

You are mixing up frameworks. [Route("myapi/[controller]/[action]")] is for asp.net-core while your code appears to be for asp.net-web-api

A few suggested changes.

Module code can be simplified

GlobalConfiguration.Configure(RegisterRoutes.Load);

Since attribute routing is configured

 config.MapHttpAttributeRoutes();

Use the correct attributes on the APIController and action

[RoutePrefix("myapi/Authorize")]
public class AuthorizeController : ApiController {
    [HttpGet, ActionName("User")]
    [Route("user")] //GET myapi/authorize/user
    [AllowAnonymous]
    public IHttpActionResult GetUser() {
        WebUser user = new WebUser();
        user.Key = Guid.Empty.ToString();
        return Ok(user);
    }
}

answered Aug 17 '18 at 15:55

Nkosi

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Thank you @Nkosi. I forgot to mention in my answer that I removed the attribute routes that I included in my question. I used the configure lambda because I will end up piping that `config` var into a couple of other calls. Also, I see that you are returning an action result type. What the pro/con on just returning the type directly? I have updated the serializers so that I the framework converts the types to JSON. I am currently getting a JSON response back from my API calls without using Action Result. – jwatts1980 Aug 17 '18 at 18:55
1

@jwatts1980 using the action result allows more flexibility for returning different http responses. using the plain object will always return HTTP 200 OK unless an exception is thrown. – Nkosi Aug 17 '18 at 19:30
Thank you for your answer. It was very helpful. I have updated to However, adding the `new { }` declaration to the `defaults` and `constraints` parameters as indicated by my answer was what finally made it start working. – jwatts1980 Aug 18 '18 at 20:00

jwatts1980 · Accepted Answer · 2018-08-17T18:49:55.133

Turns out the problem was in the MapHttpRoute() method call. It seems that the routing does not like not having a value for the defaults and constraints parameters. I updated the map call to this:

config.Routes.MapHttpRoute(
    name: "DefaultApi", 
    routeTemplate: Constants.ApiBaseRoute + "/{controller}/{action}",
    defaults: new {  }, 
    constraints: new {  }
);

I also had to add the action template parameter. And I removed the route attributes on the controller.

404 Errors for WebAPI - Registering routes in HttpModule not working

2 Answers2