Property injection in to Web Api controller using Autofac - asp.net-web-api

Question

I'm trying to set a property on an System.Web.Http.ApiController to a value of a resolved IServerPackageRepository. The controller runs in a HttpSelfHostServer and the DependencyResolver has been set to AutofacWebApiDependencyResolver. Here is the code from the Autofac.Module.Load method
...
builder.RegisterType<ServerPackageRepository>()
.As<IServerPackageRepository>()
.SingleInstance()
.WithParameter("path", this.StoragePath);
builder.RegisterApiControllers(Assembly.GetExecutingAssembly())
.PropertiesAutowired();
The ApiController controller itself has a property of type
public IServerPackageRepository Repository { get; set; }
but is never resolved.
I am trying to do it this way because ApiController won't take nothing but default constructors. Any suggestions on how to do this the correct way using Autofac?

Answer 1

If the ApiController is only using the default constructor is sounds like the dependency resolver is not being called and may not be registered with Web API correctly. Here is a working example of self-hosting with constructor injection.
The dependency (in this case a simple logger):
public interface ILogger
{
void Log(string text);
}
public class Logger : ILogger
{
public void Log(string text)
{
Debug.WriteLine(text);
}
}
A simple controller with a dependency on the logger:
public class ValuesController : ApiController
{
readonly ILogger _logger;
public ValuesController(ILogger logger)
{
_logger = logger;
}
// GET api/values
public IEnumerable<string> Get()
{
_logger.Log("GET api/values");
return new string[] { "value1", "value2" };
}
}
The console application:
class Program
{
static void Main(string[] args)
{
var configuration = new HttpSelfHostConfiguration("http://localhost:8080");
configuration.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{id}",
defaults: new { id = RouteParameter.Optional }
);
var builder = new ContainerBuilder();
// Register API controllers using assembly scanning.
builder.RegisterApiControllers(Assembly.GetExecutingAssembly());
// Register API controller dependencies.
builder.Register<ILogger>(c => new Logger()).SingleInstance();
var container = builder.Build();
// Set the dependency resolver implementation.
var resolver = new AutofacWebApiDependencyResolver(container);
configuration.DependencyResolver = resolver;
// Open the HTTP server and listen for requests.
using (var server = new HttpSelfHostServer(configuration))
{
server.OpenAsync().Wait();
Console.WriteLine("Hosting at http://localhost:8080/{controller}");
Console.ReadLine();
}
}
}
Hit the controller action using:
http://localhost:8080/api/values
Please test this out and let me know if you have any problems.

Answer 2

Not sure if this is what you want but you can create your own base controller and inject the IServerPackageRepository into it.
public class MyApiController : ApiController {
public IServerPackageRepository ServerPackageRepository { get; set; }
public MyApiController(IServerPackageRepository serverPackageRepository) {
ServerPackageRepository = serverPackageRepository;
}
}
Then, use this as your base controller:
public class ProductsController : MyApiController {
public ProductsController(IServerPackageRepository serverPackageRepository)
: base(serverPackageRepository) {
}
public IEnumerable<Product> Get() {
ServerPackageRepository.DoWork();
//...
}
}

Answer 3

An alternative would be to directly wire your dependency to the property like so:
var repo = new ServerPackageRepository(path: this.StoragePath);
builder.RegisterInstance(repo)
.SingleInstance();
builder.RegisterApiControllers(Assembly.GetExecutingAssembly())
.WithProperty("Repository", repo)
.PropertiesAutowired();