Injecting Dependency into Web API Controller - asp.net-mvc-4

Question

I want to inject unity container into WebController.
I have UnityDependencyResolver:
public class UnityDependencyResolver : IDependencyResolver
{
readonly IUnityContainer _container;
public UnityDependencyResolver(IUnityContainer container)
{
this._container = container;
}
public object GetService(Type serviceType)
{
try
{
return _container.Resolve(serviceType);
}
catch
{
return null;
}
}
public IEnumerable<object> GetServices(Type serviceType)
{
try
{
return _container.ResolveAll(serviceType);
}
catch
{
return new List<object>();
}
}
public void Dispose()
{
_container.Dispose();
}
}
Then, in my Global.asax I add the following line:
var container = new UnityContainer();
container.RegisterType<IService, Service>
(new PerThreadLifetimeManager()).RegisterType<IDALContext, DALContext>();
DependencyResolver.SetResolver(new UnityDependencyResolver(container));
Then, If I use the following in a Web Controller:
private IService _service;
public HomeController(IService srv)
{
_service = srv;
}
It works fine.
But I want to inject it into WebAPI Controller, so if I do it the same way:
private IService _service;
public ValuesController(IService srv)
{
_service = srv;
}
It does not work, it says that constructor is not defined.
Ok, I create one more constructor:
public ValuesController(){}
And in this case it uses only this constructor and never the one where I should inject unity container.
Please advise.

Answer 1

Add this in your WebApiConfig:
public static class WebApiConfig
{
public static void Register(HttpConfiguration config)
{
// Routes and other stuff here...
var container = IocContainer.Instance; // Or any other way to fetch your container.
config.DependencyResolver = new UnityDependencyResolver(container);
}
}
And if you want the same container you can keep it in a static variable, like so:
public static class IocContainer
{
private static readonly Lazy<IUnityContainer> Container = new Lazy<IUnityContainer>(() =>
{
var container = new UnityContainer();
return container;
});
public static IUnityContainer Instance
{
get { return Container.Value; }
}
}
More info can be found here:
http://www.asp.net/web-api/overview/advanced/dependency-injection
On a sidenote, I can also recommend the nuget-package Unity.Mvc. It adds a UnityWebActivator and support for PerRequestLifetimeManager.
https://www.nuget.org/packages/Unity.Mvc/