Is it possible to create hierarchical enums?

Question

I want to create a hierarchical enum that represents a type that I can pass as a parameter.

The data structure looks like this:

enum Cars
{
   Ford { Corsair, Cortina, Galaxy, GT },
   Ferrari { Testarossa, California, Enzo },
   ...
}

I wish to call a function with the following signature:

public void BuildCar(Cars car);

Like this:

BuildCar(Cars.Ferrari.Enzo);

Basically, I want to enforce the car/manufacturer relationship in the type.

Answer 1

I thought about answering this with extensions and/or ICustomEnum stuff.

Then I thought - is there anything really that bad with the following? :-)

    enum Cars
    {
       Ford_Corsair,
       Ford_Cortina,
       Ford_Galaxy,
       Ford_GT,

       Ferrari_Testarossa,
       Ferrari_California,
       Ferrari_Enzo,
    }

Your function still looks like:

public void BuildCar(Cars car);

Your call looks like:

BuildCar(Cars.Ferrari_Enzo);

Answer 2

Do-it-yourself solution:

class Cars
{
    private static int CurrentId = 0;

    private readonly int id;

    private Cars()
    {
        id = CurrentId;
        CurrentId++;
    }

    public static class Ford
    {
        public static Cars Corsair = new Cars();
        public static Cars Cortina = new Cars();
        public static Cars Galaxy = new Cars();
        public static Cars GT = new Cars();
    }

    public static class Ferrari
    {
        public static Cars Testarossa = new Cars();
        public static Cars California = new Cars();
        public static Cars Enzo = new Cars();
    }

    // Add overrides of Equals and GetHash from id
}

You will lose all features contained in Enums class this way. But that is understandable, because you want logic that is not normally supported.