Is there any HttpControllerBuilder for ASP.NET Web API? - dependency-injection

Question

If I want to implement a Dependency Injection for ASP.NET MVC controllers, I can use IControllerFactory interface to create a factory class and then register it in Global.asax.cs, like:
ControllerBuilder.Current.SetControllerFactory(controllerFactory)
(reference: http://www.dotnetcurry.com/ShowArticle.aspx?ID=786)
Now my question is:
How could I set a factory for an IHttpControllerActivator derived class?
Do we have something in ASP.NET MVC 4.0 like:
HttpControllerBuilder.Current.SetApiControllerActivator(httpControllerActivator)
?
Update:
I want to add my current code, it might be helpful to understand the case:
My customized HttpControllerActivator:
public class MyCustomApiActivator : DefaultHttpControllerActivator
//or IHttpControllerActivator ?
{
private readonly Dictionary<string, Func<HttpRequestMessage, IHttpController>> _apiMap;
public MyCustomApiActivator(IMyRepository repository)
{
if (repository == null)
{
throw new ArgumentException("repository");
}
_apiMap = new Dictionary<string, Func<HttpRequestMessage, IHttpController>>();
controllerMap["Home"] = context => new HomeController();
_apiMap["MyCustomApi"] = context => new MyCustomApiController(repository);
}
public IHttpController Create(HttpRequestMessage request, HttpControllerDescriptor controllerDescriptor, Type controllerType)
{
if(_apiMap.ContainsKey(controllerType.Name))
return _apiMap[controllerType.Name](request);
return null;
}
}
My composition root:
public class CompositionRoot
{
private readonly IHttpControllerActivator _apiControllerActivator;
public CompositionRoot()
{
_apiControllerActivator = CompositionRoot.CreateHttpControllerActivator();
}
public IHttpControllerActivator ApiControllerActivator
{
get { return _apiControllerActivator; }
}
private static IHttpControllerActivator CreateHttpControllerActivator()
{
string defaultRepositoryTypeName = ConfigurationManager.AppSettings["DefaultRepositoryTypeName"];
var defaultRepositoryType = Type.GetType(defaultRepositoryTypeName, true);
var defaultRepository = (IMyRepository)Activator.CreateInstance(defaultRepositoryType);
var apiController = new MyCustomApiActivator(defaultRepository);
return apiController;
}
}
Finally this is inside my Global.asax.cs, where I need a trick:
protected void Application_Start()
{
AreaRegistration.RegisterAllAreas();
WebApiConfig.Register(GlobalConfiguration.Configuration);
FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
RouteConfig.RegisterRoutes(RouteTable.Routes);
BundleConfig.RegisterBundles(BundleTable.Bundles);
var root = new CompositionRoot();
//The following line raise this compile-time error:
// cannot convert from 'System.Web.Http.Dispatcher.IHttpControllerActivator'
// to 'System.Web.Mvc.IControllerFactory'
ControllerBuilder.Current.SetControllerFactory(root.ApiControllerActivator);
}

Answer 1

Mark Seemann, author of Dependency Injection in .NET, has a short series on DI with ASP.NET WebAPI.
He places the composition root inside an IHttpControllerActivator
Dependency Injection and Lifetime Management with ASP.NET Web API
Dependency Injection in ASP.NET Web API with Castle Windsor
Maybe that helps.
Update
GlobalConfiguration.Configuration.Services.Replace(
typeof(IHttpControllerActivator),
new PoorMansCompositionRoot());
Registers your custom HttpControllerActivator globally.

Answer 2

In ASP.NET Web API HttpControllerDispatcher is responsible for constructing controllers. It works with the DependecyResolver by default but if you want to extend its functionality, you need to override its SendAsync method and register it again.
Example:
public class MyCustomDispatcher : HttpControllerDispatcher {
protected override Task<HttpResponseMessage> SendAsync(
HttpRequestMessage request,
CancellationToken cancellationToken) {
// Do your stuff here
// According to your requirements, either run its default functionality
// or return your own stuff
return base.SendAsync(request, cancellationToken);
}
}
Note:
However, I wasn't able to find an elegant way to replace the default one
globally. You can replace the default one per-route easily by
attaching this custom dispatcher to a route but there seems to be no
way to do this globally. I opened up a discussion on that at the
project site: http://aspnetwebstack.codeplex.com/discussions/400366