Autofac：注册类型，其中参数取决于 ApiController 的属性

Question

I want to register Repository with Autofac so that it is the same as in parameterless constructor? Which I then intend to remove. Example code:

public class GroupController : ApiController
{
    protected IRepository Repository;
    protected ISettings Settings;

    protected GroupController()
    {
        Settings = new Settings();
        Repository = new Repository(User.Identity.IsAuthenticated ? Settings.ConfigAuth : Settings.Config)
    }

    public GroupController(ISettings settings, IRepository repository)
    {
        Repository = repository;
        Settings = settings;
    }
}

This is an api controller in .Net framework. Settings are written in web.config. This is how autofac config looked like before I had only one config.

var builder = new ContainerBuilder();
builder.RegisterApiControllers(Assembly.GetExecutingAssembly());
var settings = new Settings();
Builder.RegisterType<Repository>()
   .As<IRepository>()
   .WithParameter(new TypedParameter(typeof(RepoConfig), settings.Config))
   .InstancePerRequest();

There is currently only one implementation of IRepository.

public class Repository : IRepository
{
   private readonly RepoConfig _config;

   public(RepoConfig config)
   {
      _config = config;
   }
}

Answer 1

You can use Lambda Registrations. From Autofac documentation

You can register components using lambda expressions and make a runtime choice right in the registration for how to handle things. Note this may have an effect on performance depending on the expense of the runtime check and how often it gets executed, but it's an option.

http://docs.autofac.org/en/latest/register/registration.html (Check lambda expression components)

Based on your example using Lambda Registrations, you can do autofac reg as below (I have not tested)

        var builder = new ContainerBuilder();

        builder.Register(c => new Settings()).As<ISettings>();

        builder.Register<Repository>((c) =>
            {
                ISettings s = c.Resolve<ISettings>();
                Settings repoSettings = User.Identity.IsAuthenticated ? s.ConfigAuth : s.Config;
                return new Repository(repoSettings);
            }
        )
       .As<IRepository>()
       .InstancePerRequest();

        Container = builder.Build();

Then remove your parameter-less constructor and add

public GroupController(IRepository repository)
{
    Repository = repository;
}

hope it helps.

Answer 2

I implemented an workaround for this implementation. Not the best way but it works. This way initialization of Repository doesn't need parameter and I set it with a propertie in constructor of Controller.

public class GroupController : ApiController
{
    protected IRepository Repository;
    protected ISettings Settings;

    public GroupController(ISettings settings, IRepository repository)
    {
        Settings = settings;
        Repository = repository;
        Repository.RepoConfig = User.Identity.IsAuthenticated ? Settings.ConfigAuth : Settings.Config
    }
}

public class Repository : IRepository
{
   private readonly RepoConfig _config;

   public RepoConfig RepoConfig
   {
       get => _config;
       set
       {
           _config = value;
       }
   }
   ...
}

And for autofac there is standard DI refister:

var builder = new ContainerBuilder();
builder.RegisterApiControllers(Assembly.GetExecutingAssembly());
Builder.RegisterType<Repository>()
   .As<IRepository>()
   .InstancePerRequest();