using System;

using System.Linq;

​

using System.Collections.Generic;

​

​

public class Program

{

    public static void Main()

    {

        GetTransformers(TransformerType.Decepticon).Dump();

        GetTransformersOop(TransformerType.Autobot).Dump();

    }

​

​

    public static IEnumerable<ITransformer> GetTransformersOop(TransformerType t)

    {

        if (t == TransformerType.Autobot) 

            return GetAutobots();

        else if (t == TransformerType.Decepticon)

            return GetDecepticons();

        return null;

    }

    public static List<ITransformer> GetTransformers(TransformerType t)

    {

        if (t == TransformerType.Autobot) 

            return GetAutobots().ToList<ITransformer>();

        else if (t == TransformerType.Decepticon)

            return GetDecepticons().ToList<ITransformer>();

        return null;

    }

    /*

    // Autobot (and Decepticon) implements ITransformer, very OOP;

    // yet the compiler won't allow us to return List<Autobot> to List<ITransformer>, very un-OOP

    public static List<ITransformer> GetTransformersOopYetItDoesntCompile(TransformerType t)

    {

        if (t == TransformerType.Autobot)

​

​

​

​

            return GetAutobots();

        else if (t == TransformerType.Decepticon)

            return GetDecepticons();

​

        return null;

    }

    */  

    static List<Autobot> GetAutobots()

    {

        return new List<Autobot> 

        {

            new Autobot { Name = "Optimus" }

        };

    }

    static List<Decepticon> GetDecepticons()

    {

        return new List<Decepticon> 

        {

            new Decepticon { Name = "Megatron" }

        };

    }   

}

​

public interface ITransformer

{

    string Name { get; set; }

}

​

​

public enum TransformerType { Autobot = 1, Decepticon = 2 };

​

​

public class Autobot : ITransformer

{

    public string Name { get; set; }

}

​

public class Decepticon : ITransformer

{

    public string Name { get; set; }

}

​