Passing parameters to constructors using Autofac

Question

I'm very new to autofac so it's possible that I'm completely misusing it.

Let's say I have a class that has this structure:

public class HelperClass : IHelperClass
{
     public HelperClass(string a, string b)
     {
         this.A = a;
         this.B = b;
     }
}

and I have two classes that use that class, but require different defaults for the constructor. The second constructor is JUST for testing purposes -- we will always want a HelperClass in the "real" app.:

public class DoesSomething: IDoesSomething
{
     public DoesSomething()
         : this(new HelperClass("do", "something"));
     {

     }

     internal DoesSomething(IHelperClass helper)
     {
          this.Helper = helper;
     }
}

public class DoesSomethingElse : IDoesSomethingElse
{
     public DoesSomethingElse()
         : this(new HelperClass("does", "somethingelse"));
     {

     }

     internal DoesSomethingElse(IHelperClass helper)
     {
          this.Helper = helper;
     }
}

Here's my AutoFac module:

public class SomethingModule: Module
{
    protected override void Load(ContainerBuilder builder)
    {
         builder.RegisterType<DoesSomething>().As<IDoesSomething>();
         builder.RegisterType<DoesSomethingElse>().As<IDoesSomethingElse();
    }
}

My question(s):

1. When I call resolve on DoesSomething or DoesSomethignElse -- will it resolve the internal constructor instead of the public one? Do I need to leave IHelperClass unregistered?
2. If yes, how do I make it pass different parameters to each instance of IHelperClass depending on whether it's used in DoesSomething or DoesSomethingElse?

Answer 1

You can always use the WithParameter method to explicitly specify a constructor parameter:

builder.RegisterType<DoesSomething>()
       .As<IDoesSomething>()
       .WithParameter("helper", new HelperClass("do", "something"));

builder.RegisterType<DoesSomethingElse>()
       .As<IDoesSomethingElse>()
       .WithParameter("helper", new HelperClass("do", "somethingelse"));

As far as I can tell there is no need for an interface for HelperClass because it essentially is just a value holder.

For this to work you would need to make the internal constructor public, I think.