immutable-polymorphism.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Immutable
{
    public struct PartyName
    {
        public string Name { get; }

        public PartyName(string name)
        {
            Name = name;
        }
    }

    public struct PartyCode
    {
        public string Code { get; }

        public PartyCode(string code)
        {
            Code = code;
        }
    }

    public abstract class Party<T>
        where T : Party<T>
    {
        public PartyName Name { get; }

        public PartyCode Code { get; }

        public abstract T WithName(PartyName name);

        public abstract T WithCode(PartyCode code);

        protected Party(PartyName name, PartyCode code)
        {
            Name = name;
            Code = code;
        }

        protected Party(Party<T> original)
        {
            Name = original.Name;
            Code = original.Code;
        }

        protected Party(Party<T> original, PartyName name)
        {
            Name = name;
            Code = original.Code;
        }

        protected Party(Party<T> original, PartyCode code)
        {
            Name = original.Name;
            Code = code;
        }
    }

    public struct PersonAge
    {
        public int Age { get; }

        public PersonAge(int age)
        {
            Age = age;
        }
    }

    public class Person : Party<Person>
    {
        public PersonAge Age { get; }

        public Person(PartyName name, PartyCode code, PersonAge age)
            : base(name, code)
        {
            Age = age;
        }

        public Person WithAge(PersonAge age)
        {
            return new Person(this, age);
        }

        public override Person WithName(PartyName name)
        {
            return new Person(this, name);
        }

        public override Person WithCode(PartyCode code)
        {
            return new Person(this, code);
        }

        protected Person(Person original, PartyName name)
            : base(original, name)
        {
            Age = original.Age;
        }

        protected Person(Person original, PartyCode code)
            : base(original, code)
        {
            Age = original.Age;
        }

        protected Person(Person original, PersonAge age)
            : base(original)
        {
            Age = age;
        }
    }

    public struct CompanyNumber
    {
        public int Number { get; }

        public CompanyNumber(int number)
        {
            Number = number;
        }
    }

    public class Company : Party<Company>
    {
        public CompanyNumber CompanyNumber { get; }

        public Company(PartyName name, PartyCode code, CompanyNumber number)
            : base(name, code)
        {
            CompanyNumber = number;
        }

        public Company WithAge(CompanyNumber number)
        {
            return new Company(this, number);
        }

        public override Company WithName(PartyName name)
        {
            return new Company(this, name);
        }

        public override Company WithCode(PartyCode code)
        {
            return new Company(this, code);
        }

        protected Company(Company original, PartyName name)
            : base(original, name)
        {
            CompanyNumber = original.CompanyNumber;
        }

        protected Company(Company original, PartyCode code)
            : base(original, code)
        {
            CompanyNumber = original.CompanyNumber;
        }

        protected Company(Company original, CompanyNumber number)
            : base(original)
        {
            CompanyNumber = number;
        }
    }
}