OptionWithMapt

Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Security.Cryptography.X509Certificates;
using option;

namespace option {
    class Program {
        static void Main(string[] args) {
            string message;
            var option = GetOption(true);
            Console.WriteLine(EvaulateOption(option));

            var options = GetListOfOptions();
            var somes = options.OfType<Some<string>>().Select(x => x.Value);
            foreach (var some in somes) {
                Console.WriteLine(some);
            }
            
            Console.ReadLine();
        }

        static IEnumerable<Option> GetListOfOptions() {
            return new List<Option> {
                new None(),
                new Some<string>("hi"),
                new Some<string>("hello"),
                new Some<string>("hey")
            };
        }

        static Option GetOption(bool ifSome) {
            return ifSome ? new Some<string>("Hello!") : new None() as Option;
        }

        static string EvaulateOption(Option option) {
            switch (option) {
                case Some<string> s:
                    return s.Value;
                case None n:
                    return "None";
                default:
                    return "Default";
            }
        }
    }

    abstract class Option {

    }

    class Some<T> : Option {
        public T Value { get; }

        public Some(T value) {
            Value = value;
        }
    }

    class None : Option {

    }
}