How to configure Web Api 2 to look for Controllers in a separate project? (just like I used to do in Web Api)

Question

I used to place my controllers into a separate Class Library project in Mvc Web Api. I used to add the following line in my web api project\'s global.asax to look for contro

Answer 1

You need to tell webapi/mvc to load your referrenced assembly. You do that with the compilation/assemblies section in your web.config.

<compilation debug="true" targetFramework="4.5.2">
  <assemblies>
    <add assembly="XYZ.SomeAssembly" />
  </assemblies>
</compilation>

Simple as that. You can do it with code the way @user1821052 suggested, but this web.config version will have the same effect.

Answer 2

I have just confirmed that this works fine. Things to check:

References: Does your main Web API project reference the external class library?

Routing: Have you set up any routes that might interfere with the external controllers?

Protection Level: Are the controllers in the external library public?

Inheritance: Do the controllers in the external library inherit from ApiController?

Versioning: Are both your Web API project and class library using the same version of the Web API libraries?

If it helps, I can package up my test solution and make it available to you. Also, as a point to note, you don't need to tell Web API to find the controllers with the line you added to Global.asax, the system finds the controllers automatically provided you have them referenced.

Answer 3

If your class library is built with EF then make sure you have the connection string specified in the App.config for the class library project, AND in the Web.config for your Web API MVC project.

Answer 4

Are you sure that your referenced assembly was loaded BEFORE IAssembliesResolver service called? Try to insert some dummy code in your application, something like

var a = new MyClassLibraryProject.Controllers.MyClass();

in configuration method (but don`t forget, that compiler can "optimize" this code and totally remove it, if "a" is never used). I've had similar issue with assembly loading order. Ended up with force loading dependent assemblies on startup.

Answer 5

Apart from what has been said already:

Make sure you don't have two controllers of the same name in different namespaces.

Just had the case where one controller (foo.UserApiController) should be partially migrated to a new namespace (bar.UserApiController) and URI. The old controller was mapped by convention to /userapi, the new one was attribute-routed via RoutePrefix["api/users"]. The new controller didn't work until I renamed it to bar.UserFooApiController.

Answer 6

It should work as is. Checklist

• Inherit ApiController
• End controller name with Controller. E.g. ValuesController
• Make sure WebApi project and class library project reference same WebApi assemblies
• Try to force routes using attribute routing
• Clean the solution, manually remove bin folders and rebuild
• Delete Temporary ASP.NET Files folders. WebApi and MVC cache controller lookup result
• Call `config.MapHttpAttributeRoutes(); to ensure framework takes attribute routes into consideration
• Make sure that the method you are calling is made to handle correct HTTP Verb (if it is a GET web method, you can call via browser URL, if it is POST you have to otherwise craft a web request)

This controller:

[RoutePrefix("MyValues")]
public class AbcController : ApiController
{
    [HttpGet]
    [Route("Get")]
    public string Get()
    {
        return "Ok!";
    }
}

matches this url:

http://localhost/MyValues/Get (note there is no /api/ in route because it wasn't specified in RoutePrefix.

---

Controller lookup caching: This is default controller resolver. You will see in the source code that it caches lookup result.

/// <summary>
/// Returns a list of controllers available for the application.
/// </summary>
/// <returns>An <see cref="ICollection{Type}" /> of controllers.</returns>
public override ICollection<Type> GetControllerTypes(IAssembliesResolver assembliesResolver)
{
    HttpControllerTypeCacheSerializer serializer = new HttpControllerTypeCacheSerializer();

    // First, try reading from the cache on disk
    List<Type> matchingTypes = ReadTypesFromCache(TypeCacheName, IsControllerTypePredicate, serializer);
    if (matchingTypes != null)
    {
        return matchingTypes;
    }
...
}