Some/None

Option.cs

using System;

namespace OptionTypes
{
    public abstract class Option<T>
    {
        public abstract T GetSome { get; }
        public abstract override string ToString();

        protected T Value;

        public bool IsSome { get; protected set; }
        public bool IsNone { get { return !IsSome; } }

        public static Some<T> Some(T value)
        {
            return new Some<T>(value);
        }

        public static None<T> None()
        {
            return new None<T>();
        }
    }

    public sealed class Some<T> : Option<T>
    {
        public Some(T value)
        {
            if (value == null)
                throw new ArgumentNullException("value", "Argument passed to Some was null - use None<T> instead.");

            Value = value;
            IsSome = true;
        }

        public override T GetSome { get { return Value; } }

        public override string ToString()
        {
            return Value.ToString();
        }
    }

    public sealed class None<T> : Option<T>
    {
        public None()
        {
            IsSome = false;
        }

        public override T GetSome { get { throw new InvalidOperationException("No value on None<T>"); } }

        public override string ToString()
        {
            return "None";
        }
    }

    public class MyClass
    {
        public void Main()
        {
            var some = Option<string>.Some("Hello");
            var none = Option<string>.None();

            WriteDataIf(some);
            WriteDataIf(none);

            WriteDataSwitch(some);
            WriteDataSwitch(none);
        }

        private void WriteDataIf(Option<string> option)
        {
            if (option.IsSome)
            {
                Console.WriteLine(option.GetSome);
            }
            else
            {
                Console.WriteLine("Its None");
            }
        }

        private void WriteDataSwitch(Option<string> option)
        {
            switch(option.IsSome)
            {
                case true:
                    Console.WriteLine(option.GetSome);
                    break;
                default:
                    Console.WriteLine("Its None");
                    break;
            }
        }
    }
}