Autofac - Registering instance type that takes interface as parameter - api

Question

I am very new to Autofac and not able to understand the syntax for registration. I have following calsses/interfaces :
//Interface
public interface ISender
{
void Send();
}
//implementations
public class Post : ISender
{
public void Send()
{
//Post implementation
}
}
public class Email : ISender
{
public void Send()
{
//Email implementation
}
}
And a class that calls these implementations
public class Consumer
{
ISender Sender;
public Consumer(ISender sender)
{
Sender = sender
}
public void Act()
{
Sender.Send();
}
}
Now, which implementation to call is to be decided in a controller, so I tried using IIndex from this page like:
public calss PostController
{
Consumer ConsumerObject;
public PostController(IIndex<string, Consumer> consumer)
{
ConsumerObject = consumer["post"];
}
}
public class EmailController
{
Consumer ConsumerObject;
public PostController(IIndex<string, Consumer> consumer)
{
ConsumerObject = consumer["email"];
}
}
Firstly, is it correct or doable? Now the problem is I don't understand how to register in Autofac. So, How can we register Consumer and ISender in Autofac ?? Please suggest if there is any better/alternative way.

Answer 1

The way of registering components in Autofac is described widely in the documentation here. And how to use keyed services is described in the documentation you linked.
Basically you have to create ContainerBuilder, register all your components and build the container itself, based on the project type you have.
In your situation you need to use the following registrations:
var builder = new ContainerBuilder();
builder.RegisterType<Post>().Keyed<ISender>("post");
builder.RegisterType<Email>().Keyed<ISender>("email");
builder.RegisterType<Consumer>();
If you use ASP.NET WebApi (I assume that based on the fact you are using Controllers), you need to register your controllers
builder.RegisterApiControllers(Assembly.GetExecutingAssembly());
or for MVC
builder.RegisterControllers(typeof(MvcApplication).Assembly);
Now, there are various way to pick the Consumer with proper ISender implementation (I assume you want to pick proper implementation in controller).
One would be to inject IIndex<string, ISender> to Consumer class and pass the proper key string to it as well:
public class Consumer
{
ISender Sender;
public Consumer(string type, IIndex<string, ISender> sender)
{
Sender = sender[type];
}
public void Act()
{
Sender.Send();
}
}
Then, in controller you could use Func injection:
public class PostController
{
Consumer ConsumerObject;
public PostController(Func<string, Consumer> consumer)
{
ConsumerObject = consumer("post");
}
}
public class EmailController
{
Consumer ConsumerObject;
public EmailController(Func<string, Consumer> consumer)
{
ConsumerObject = consumer("email");
}
}
Another could be registering Consumer twice with Register method and resolving ISender in registration time.