Register subset of Web API controllers with simple injector

Question

I'm manually registrering a subset of my project's Web API controllers:

container.Register(typeof(ILGTWebApiController), controllerType, Lifestyle.Transient); 

Works fine. However, when I run:

GlobalConfiguration.Configuration.DependencyResolver = 
    new SimpleInjectorWebApiDependencyResolver(container);

It seems to affect all Web API controllers in the project. I would like to leave the other ones untouched by simple injector.

If I don't run the code above, simple injector will complain about my controllers not having an empty constructor (which they obviously won't, since I'm using DI).

Answer 1

Instead of replacing the IDependencyResolver, create a custom IHttpControllerActivator that resolves the controller or fallbacks to the original activator otherwise:

public sealed class MyControllerActivator : IHttpControllerActivator
{
    private readonly Container container;
    private readonly IHttpControllerActivator original;

    public MyControllerActivator(Container container, IHttpControllerActivator original)
    {
        this.container = container;
        this.original = original;
    }

    public IHttpController Create(
        HttpRequestMessage req, HttpControllerDescriptor desc, Type type)
    {
        if (type == typeof(ILGTWebApiController))
            return (IHttpController)this.container.GetInstance(type);

        return this.original.Create(req, desc, type);
    }
}

You can configure your custom MyControllerActivator as follows:

GlobalConfiguration.Configuration.Services.Replace(typeof(IHttpControllerActivator),
    new MyControllerActivator(
        container,
        GlobalConfiguration.Configuration.Services.GetHttpControllerActivator()));