Resolving conditional dependencies autofac

Question

I am trying to resolve dependencies based on a condition.

private static readonly Dictionary<string, Action<ContainerBuilder>> QRTypeDictionary = 
    new Dictionary<string, System.Action<ContainerBuilder>> () {
            { "REST" , (builder)=> builder
                                    .RegisterType<RestPublisher>()
                                    .As<Publisher>()},
            { "DB" , (builder)=> builder
                                    .RegisterType<DBPublisher>()
                                    .As<Publisher>()}
 }

I am just looking to make sure if this is the only way to resolve dependencies based on conditions. I have been using Ninject so far and am looking for something like the following:

kernel.Bind<Publisher>()
      .To<DbPublisher>()
      .When(x => Defs.AppSettings.PublisherType == "DB")

Just want to make sure I am doing the right thing with Autofac

Answer 1

I can see 3 solutions to achieve what you want.

1. Using a lambda

   builder.RegisterType<DbPublisher>().AsSelf();
   builder.RegisterType<RestPublisher>().AsSelf();
   
   builder.Register(c => { 
       switch(Defs.AppSettings.PublisherType){
           case "DB":
               c.Resolve<DbPublisher>(); 
               break; 
           case "REST":
               c.Resolve<RestPublisher>(); 
               break; 
           default:
               throw new NotSupportedException(); 
       }
   }).As<IPublisher>(); 
   

2. Using named registration

   builder.RegisterType<DbPublisher>().Named<IPublisher>("DB");
   builder.RegisterType<RestPublisher>().Named<IPublisher>("REST");
   
   builder.Register(c => {
         var index = c.Resolve<IIndex<String, IPublisher>>(); 
         return index[Defs.AppSettings.PublisherType]
   }.As<IPublisher>(); 
   

3. Conditional registration

   if Defs.AppSettings.PublisherType is defined during registration process, you can simply conditionally register your dependency :

   switch(Defs.AppSettings.PublisherType){
       case "DB":
           builder.RegisterType<DbPublisher>().As<IPublisher>();
           break; 
       case "REST":
           builder.RegisterType<RestPublisher>().As<IPublisher>(); 
           break; 
       default:
           throw new NotSupportedException(); 
   }