Replicating Scala Option

Option.cs

//Usage   

Option<String> someString = Option<String>.Some("Hi");
Option<String> noString = Option<String>.None();
Console.WriteLine(someString.Select(x => x.Length).GetOrElse(-1));
Console.WriteLine(noString.Select(x => x.Length).GetOrElse(-1));
 
//Definition

abstract class Option<T>
{
	public abstract T Get();
	public abstract bool IsEmpty();

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

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

	public Option<B> Select<B>(Func<T, B> selector)
	{
		if (IsEmpty())
		{
			return new None<B>();
		}
		else
		{
			return new Some<B>(selector(Get()));
		}
	}

	public Option<B> SelectMany<B>(Func<T, Option<B>> selector)
	{
		if (IsEmpty())
		{
			return new None<B>();
		}
		else
		{
			return selector(Get());
		}
	}

	public T GetOrElse(T defaultValue)
	{
		if (IsEmpty())
		{
			return defaultValue;
		}
		else
		{
			return Get();
		}
	}

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

		public override T Get()
		{
			throw new NoValueException();
		}

		public override bool IsEmpty()
		{
			return true;
		}
	}

	class Some<T> : Option<T>
	{
		private T val;

		public Some(T t)
		{
			this.val = t;
		}

		public override T Get()
		{
			return val;
		}

		public override bool IsEmpty()
		{
			return false;
		}
	}

	class NoValueException : Exception
	{
	}
}