using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        IParent p = new Parent();

        Son s = new Son();

        IDaughter d = new Daughter();

        //Console.WriteLine(GetSome(p));

        //Console.WriteLine(GetSome(s));

        //Console.WriteLine(GetSome(d));

        Family f = new Family();

        List<IParent> lp = new List<IParent>();

        List<Son> ls = new List<Son>();

        s.Name = "Jeroen";

        ls.Add(s);

        //Console.WriteLine(GetSomeList(ls));

        Console.WriteLine(GetSomeLists(ls));

        Console.WriteLine(s.Name);

    }

    public static string GetSome(IParent p)

    {

        return p.GetIt();

    }

    public static string GetSomeList(IEnumerable<ISon> s)

    {

        var lp = new List<IParent>();

        foreach(var _s in s)

        {

            lp.Add(_s);

        }

        return GetSomeLists(lp);

    }

    public static string GetSomeLists(IEnumerable<IParent> p)

    {

        var list = p.ToList();

        list.Add(new Daughter());

        p = list.AsEnumerable<IParent>();

        string returnValue = string.Empty;

        foreach(var _p in p)

        {

            returnValue += _p.GetIt();

        }

        return returnValue;

    }

}

​

public class Family

{

    public Family()

    {

    }

    public IList<IParent> parents { get; set; }

    public IList<ISon> sons { get; set; }

    public IList<IDaughter> daughter { get; set; }

}

​

public interface IParent

{

    string GetIt();

}

​

public interface ISon : IParent

{

    string GetMe();

    string Name { get; set; }

}

​

public interface IDaughter : IParent

{

    string GetYou();

}

​

public class Parent : IParent

{

    public string GetIt()

    {

        return "Parent";

    }

}

​

public class Son : ISon

{

    public string GetIt()

    {

        return "Son";

    }

    public string GetMe()

    {

        return "Son";

    }

    public string Name { get; set; }

}

​

public class Daughter : IDaughter

{

    public string GetIt()

    {

        return "Daughter";

    }

    public string GetYou()

    {

        return "Daughter";

    }

}