mapping2.cs

namespace Scratch
{
    public class Tester
    {
        public class Taco<T>
        {
            public T Filling { get; set; }

            public Taco(T value)
            {
                Filling = value;
            }
        }

        public class Burrito<T>
        {
            public T Filling { get; set; }

            public Burrito(T value)
            {
                Filling = value;
            }
        }

        public class Tray<TItem1, TItem2>
        {
            public TItem1 Item1 { get; set; }
            public TItem2 Item2 { get; set; }

            public Tray(TItem1 item1, TItem2 item2)
            {
                Item1 = item1;
                Item2 = item2;
            }
        }

        #region Static Creators
        public static class Tray
        {
            public static Tray<TItem1, TItem2> Create<TItem1, TItem2>(TItem1 item1, TItem2 item2)
            {
                return new Tray<TItem1, TItem2>(item1, item2);
            }
        }

        public static class Taco
        {
            public static Taco<T> Create<T>(T value)
            {
                return new Taco<T>(value);
            }
        }

        public static class Burrito
        {
            public static Burrito<T> Create<T>(T value)
            {
                return new Burrito<T>(value);
            }
        }
        #endregion

        public static Tray<TItem1Out, TItem2Out> ConvertTray<TItem1In, TItem1Out, TItem2In, TItem2Out>(
            Tray<TItem1In, TItem2In> original,
            Func<TItem1In, TItem1Out> item1Mapper,
            Func<TItem2In, TItem2Out> item2Mapper)
        {
            return Tray.Create(
                item1Mapper(original.Item1),
                item2Mapper(original.Item2));
        }

        public void Scratch()
        {
            var quesoTaco = Taco.Create(new ChickenQueso());
            var fajitaTaco = Taco.Create(new SteakFajita());

            var withTacos = Tray.Create(quesoTaco, fajitaTaco);

            // would be nice to only have to specify Burrito.Create once ;)
            // I think _THIS_ is the part C# won't let me do
            var withBurritos = ConvertTray(withTacos, Burrito.Create, Burrito.Create);
        }
    }

    public class SteakFajita{}
    public class ChickenQueso{}
}