Step by step implementation of Option type in C#

Option.cs

using System;

namespace Option
{
    public abstract class Option<T>
    {
        public abstract T Value { get; }

        public abstract bool IsSome { get; }

        public abstract bool IsNone { get; }

        public abstract Option<TResult> Map<TResult>(Func<T, TResult> func);

        public abstract TResult Match<TResult>(Func<T, TResult> someFunc, Func<TResult> noneFunc);
    }

    public sealed class None<T> : Option<T>
    {
        public None()
        {
        }

        public override T Value
        {
            get { throw new System.NotSupportedException("There is no value"); }
        }

        public override bool IsSome { get { return false; } }

        public override bool IsNone { get { return true; } }

        public override Option<TResult> Map<TResult>(Func<T, TResult> func)
        {
            return new None<TResult>();
        }

        public override TResult Match<TResult>(Func<T, TResult> someFunc, Func<TResult> noneFunc)
        {
            return noneFunc();
        }
    }

    public sealed class Some<T> : Option<T>
    {
        private T value;

        public Some(T value)
        {
            if (value == null)
            {
                throw new System.ArgumentNullException("value", "Some value was null, use None instead");
            }

            this.value = value;
        }

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

        public override bool IsSome { get { return true; } }

        public override bool IsNone { get { return false; } }

        public override Option<TResult> Map<TResult>(Func<T, TResult> func)
        {
            return new Some<TResult>(func(value));
        }

        public override TResult Match<TResult>(Func<T, TResult> someFunc, Func<TResult> noneFunc)
        {
            return someFunc(value);
        }
    }
}