"The type IUnitOfWork does not have an accessible constructor" with Umbraco 6.1, UmbracoApiController (Web API) & Dependency Injection (Unity)

Question

I am using Umbraco 6.1 with an UmbracoApiController which has a IUnitOfWork injected into it's constructor. To inject the dependencies, I am using Unity, like I have in the past with standard Web API projects. Normally, I set unity up in the Global.asax.cs. As Umbraco does not have this I have created my own UmbracoEvents handler, which inherits from IApplicationEventHandler, and has the methods:

1. OnApplicationInitialized
2. OnApplicationStarting
3. OnApplicationStarted
4. ConfigureApi

In the OnApplicationStarted method I set up my EF database, db initializer etc and call ConfigureApi to set up Unity. My OnApplication Started and ConfigureApi methods looks like this:

    public void OnApplicationStarted(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
    {
        _applicationContext = applicationContext;
        _umbracoApplication = umbracoApplication;
        _contentService = ApplicationContext.Current.Services.ContentService;
        this.ConfigureApi(GlobalConfiguration.Configuration);
        Database.SetInitializer(null);
        PropertySearchContext db = new PropertySearchContext();
        db.Database.Initialize(true);
    }

    private void ConfigureApi(HttpConfiguration config)
    {
        var unity = new UnityContainer();
        unity.RegisterType<PropertiesApiController>();
        unity.RegisterType<IUnitOfWork, UnitOfWork>(new HierarchicalLifetimeManager());
        config.DependencyResolver = new IoCContainer(unity);
    }

My Controller code:

public class PropertiesApiController : UmbracoApiController
{
    private readonly IUnitOfWork _unitOfWork;

    public PropertiesApiController(IUnitOfWork unitOfWork)
    {
        if(null == unitOfWork)
            throw new ArgumentNullException();
        _unitOfWork = unitOfWork;
    }

    public IEnumerable GetAllProperties()
    {
        return new[] {"Table", "Chair", "Desk", "Computer", "Beer fridge"};
    }
}

My Scope Container/IoC Container code: (as per http://www.asp.net/web-api/overview/extensibility/using-the-web-api-dependency-resolver)

public class ScopeContainer : IDependencyScope
{
    protected IUnityContainer container;

    public ScopeContainer(IUnityContainer container)
    {
        if (container == null)
        {
            throw new ArgumentNullException("container");
        }
        this.container = container;
    }

    public object GetService(Type serviceType)
    {
        if (container.IsRegistered(serviceType))
        {
            return container.Resolve(serviceType);
        }
        else
        {
            return null;
        }
    }

    public IEnumerable<object> GetServices(Type serviceType)
    {
        if (container.IsRegistered(serviceType))
        {
            return container.ResolveAll(serviceType);
        }
        else
        {
            return new List<object>();
        }
    }

    public void Dispose()
    {
        container.Dispose();
    }
}

public class IoCContainer : ScopeContainer, IDependencyResolver
{
    public IoCContainer(IUnityContainer container)
        : base(container)
    {
    }

    public IDependencyScope BeginScope()
    {
        var child = this.container.CreateChildContainer();
        return new ScopeContainer(child);
    }
}

My IUnitOfWork code:

public interface IUnitOfWork : IDisposable
{
    GenericRepository<Office> OfficeRepository { get; }
    GenericRepository<Property> PropertyRepository { get; }
    void Save();
    void Dispose(bool disposing);
    void Dispose();
}

My UnitOfWork implementation:

public class UnitOfWork : IUnitOfWork
{
    private readonly PropertySearchContext _context = new PropertySearchContext();
    private GenericRepository<Office> _officeRepository;
    private GenericRepository<Property> _propertyRepository;

    public GenericRepository<Office> OfficeRepository
    {
        get
        {

            if (this._officeRepository == null)
            {
                this._officeRepository = new GenericRepository<Office>(_context);
            }
            return _officeRepository;
        }
    }
    public GenericRepository<Property> PropertyRepository
    {
        get
        {

            if (this._propertyRepository == null)
            {
                this._propertyRepository = new GenericRepository<Property>(_context);
            }
            return _propertyRepository;
        }
    }

    public void Save()
    {
        _context.SaveChanges();
    }

    private bool disposed = false;

    public virtual void Dispose(bool disposing)
    {
        if (!this.disposed)
        {
            if (disposing)
            {
                _context.Dispose();
            }
        }
        this.disposed = true;
    }

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }
}

I have used unity/DI with MVC4/WebAPI controllers and this implementation of UnitOfWork many times before without issue, so I'm thinking it's Umbraco specific.

I have also debugged the application and made sure that it hits OnApplicationStarted and that its parameters are not null.

The GetAllProperties method in the controller is just a test method to make sure it is all working fine, however, when I try and access this action I get the error:

"The type IUnitOfWork does not have an accessible constructor"

Does anyone have experience with using Umbraco 6.1 and it's UmbracoApiController with dependency injection/Unity?

Also, on an unrelated note, is there a way to return JSON instead of XML in the action? In Web API you would just define the formatter in the WebApi.config but there is none in Umbraco.

Thanks, Justin

Answer 1

In case you haven't found a solution to your problem? Download this nuget package and right after building your unity container:

GlobalConfiguration.Configuration.DependencyResolver =
   new Unity.WebApi.UnityDependencyResolver(Bootstrapper.Container);

Notice the namespace which is different than Unity.Mvc4.UnityDependencyResolver.