Question

Is there a way in Autofac to register a type with a factory delegate that gets called when that type is requested?
Something like this:

builder.RegisterType<MyType>().AsSelf()
       .WithFactory((IMyService s, ISomeDependency d) =>
                    {
                        var p1 = s.DoSomething();
                        var p2 = d.DoSomething(p1, true);
                        return new MyType(p1, p2);
                    });

Answer 1

This is probably not quite you expect, but does do the trick:

builder.Register<MyType>(container =>
{
    var s = container.Resolve<IMyService>();  
    var d = container.Resolve<ISomeDependency>();

    var p1 = s.DoSomething();
    var p2 = d.DoSomething(p1, true);
    return new MyType(p1, p2);
});

Or if you want to use automatic (constructor) injection, you can create a MyType subclass (inside the Composition Root), that takes the two dependencies. This type can easily be registered:

builder.RegisterType<AutofacMyType().As<MyType>();

// Define inside Composition Root
private sealed class AutofacMyType : MyType
{
    public AutofacMyType(IMyService s, ISomeDependency d)
        : this(s.DoSomething(), d) { }

    private AutofacMyType(Something p1, ISomeDependency d)
        : base(p1, d.DoSomething(p1, true)) { }
}