Roman To Arabic

RomanArabic.cs

using System;
using NUnit.Framework;

namespace RomanTest
{
	public class RomanArabic
	{
		public RomanArabic() { }

		[TestCase("M", 1000)]
		[TestCase("D", 500)]
		[TestCase("I", 1)]
		[TestCase("II", 2)]
		[TestCase("IV", 4)]
		[TestCase("IX", 9)]
		[TestCase("XI", 11)]
		[TestCase("XIX", 19)]
		[TestCase("XCIX", 99)]
		[TestCase("MCMXLIX", 1949)]
		public void RomanArabicTest(String roman, int arabic)
		{
			var result = new Romanumberal().ConvertToArabic(roman);
			Assert.That(result, Is.EqualTo(arabic));
		}
	}
}

Romanumberal.cs

using System;
using System.Collections.Generic;

namespace RomanTest
{
	public class Romanumberal
	{
		private Dictionary<char, int> romanarabic = new Dictionary<char, int>() {
			{'M', 1000},
			{'D', 500},
			{'C', 100},
			{'L', 50},
			{'X', 10},
			{'V', 5},
			{'I', 1},
		};

		public int ConvertToArabic(String roman)
		{
			var total = 0;
			var chars = roman.ToCharArray();

			for (int i = 0; i < chars.Length; i++) {
				bool isNotLastChar 	= i < chars.Length - 1;
				int currentIndexValue	= romanarabic[chars[i]];
				int nextIndexValue 	= isNotLastChar ? romanarabic[chars[i + 1]] : 0;
				int counter 		= currentIndexValue < nextIndexValue ? -1 : 1;

				total += (currentIndexValue * counter);
			}

			return total;
		}
	}
}