Registering a named type with autofac and using the name for string parameter

Question

I have the following registrations (note that I haven't finished this code yey, so it may not even work as expected):

builder.RegisterType<SimpleInMemoryChannel>()
    .Named<IChannel>("ErrorChannel")
    .WithParameter(new NamedParameter("channelName", "ErrorChannel"));
builder.RegisterType<SimpleInMemoryChannel>()
    .Named<IChannel>("RequestCbrInput")
    .WithParameter(new NamedParameter("channelName", "RequestCbrInput"));

// Constructor: public SimpleInMemoryChannel(string channelName)

As you can see, I'm trying to use the name of the registered object for the channelName value. The code is a bit verbose. Is there some way I can have that assignment happen automatically? eg I'd like to just write:

builder.RegisterType<SimpleInMemoryChannel>()
    .Named<IChannel>("ErrorChannel");
builder.RegisterType<SimpleInMemoryChannel>()
    .Named<IChannel>("RequestCbrInput");

and have the channelName set automatically.

Answer 1

There is nothing in the default functionality which would allow this to happen. You will either need to customise your registration, or your resolving using a factory. The simplest solution is the one you mentioned in your comment - add a helper function for registering the channel - that way you can still use the default resolution process.

Answer 2

Having a RegisterChannel method may be the more elegant solution.

By the way, if you can't have such a method you can use a custom module :

public class NamedParameterModule<TServiceType> : Module
{
    private readonly string _parameterName;

    public NamedParameterModule(String parameterName)
    {
        this._parameterName = parameterName;
    }

    protected override void AttachToComponentRegistration(
        IComponentRegistry componentRegistry, IComponentRegistration registration)
    {
        KeyedService keyedService = registration.Services
            .OfType<KeyedService>()
            .FirstOrDefault(ks => ks.ServiceType == typeof(TServiceType));

        if (keyedService != null)
        {
            registration.Preparing += (sender, e) =>
            {
                e.Parameters = e.Parameters.Concat(new Parameter[] { 
                    new NamedParameter(this._parameterName, keyedService.ServiceKey)
                });
            };
        }

        base.AttachToComponentRegistration(componentRegistry, registration);
    }
}

And register it using builder.RegisterModule(new NamedParameterModule<IFoo>("channelName"));

This this dotnetfiddle for live example : https://dotnetfiddle.net/MPfMup .