Configuring an Autofac delegate factory that's defined on an abstract class

Question

I\'m working on a C# project. I\'m trying to get rid of a Factory class that has a large switch statement.

I want to configure Autofac to be able to con

Answer 1

What you're looking for is the IIndex<,> Relationship Type.

If you register your sub-classes with .Keyed<>(...) you can key a registration to a value (object).

For example:

builder.RegisterType<SprocketWidget>()
   .Keyed<Widget>(WidgetType.Sproket)
   .InstancePerDependency();

builder.RegisterType<WhizbangWidget>()
   .Keyed<Widget>(WidgetType.Whizbang)
   .InstancePerDependency();

Then you only require a dependency of IIndex<WidgetType,Widget> to mimic factory behaviour.

public class SomethingThatUsesWidgets
{    
    private readonly IIndex<WidgetType,Widget> _widgetFactory;
    public SomethingThatUsesWidgets(IIndex<WidgetType,Widget> widgetFactory)
    {
        if (widgetFactory == null) throw ArgumentNullException("widgetFactory");
        _widgetFactory = widgetFactory;
    }

    public void DoSomething()
    {
        // Simple usage:
        Widget widget = widgetFactory[WidgetType.Whizbang];

        // Safe Usage:
        Widget widget2 = null;
        if(widgetFactory.TryGetValue(WidgetType.Sprocket, out widget2))
        {
            // do stuff
        }
    }
}

That's using Dependency Injection approach, if you just want to resolve the factory:

var factory = Container.Resolve<IIndex<WidgetType,Widget>>();