NinjectKernelActivator.cs

using System;
using System.Net.Http;
using System.Web.Http.Controllers;
using System.Web.Http.Dispatcher;
using Ninject;

namespace WebApiNinjectIHttpControllerActivator
{
    public class NinjectKernelActivator: IHttpControllerActivator
    {
        private readonly IKernel _kernel;

        public NinjectKernelActivator(IKernel kernel)
        {
            _kernel = kernel;
        }

        public IHttpController Create(HttpRequestMessage request, HttpControllerDescriptor controllerDescriptor, Type controllerType)
        {
            var controller = (IHttpController) _kernel.Get(controllerType);

            request.RegisterForDispose( new Release(()=> _kernel.Release(controller)));

            return controller;
        }
    }

    internal class Release : IDisposable
    {
        private readonly Action _release;

        public Release(Action release)
        {
            _release = release;
        }

        public void Dispose()
        {
            _release();
        }
    }
}

Hvorfor benytte IHttpControllerActivator og ikke IDependencyResolver i ASP.NET WebApi:

http://blog.ploeh.dk/2012/09/28/DependencyInjectionAndLifetimeManagementWithASPNETWebAPI.aspx