[PluginFamily("Default")]
public interface IWidget1

[Pluggable("Default")]
public class Widget1 : IWidget1

[PluginFamily("Default")]
public interface IAnotherWidget

[Pluggable("Default")]
public class AnotherWidget : IAnotherWidget
{
    public AnotherWidget(IWidget widget)
    {
       ...
    }
}

IAnotherWidget _anotherWidget = ObjectFactory.GetInstance<IAnotherWidget>();