DynamicChangeHelper.cs

using System;
using System.Collections.Generic;
using System.Linq;

namespace CoinChangeProblem
{
    public static class DynamicChangeHelper
    {
        public static int MinimalChangeForCoin(int coin, IEnumerable<int> coins)
        {
            if (coin <= 0)
            {
                throw new IndexOutOfRangeException("Coin cannot be lesser or equal to zero.");
            }

            var coinsAsArray = coins.ToArray();

            if (coinsAsArray.Length == 0)
            {
                throw new IndexOutOfRangeException("Coins array cannot be empty.");
            }

            var coinsContainOne = coinsAsArray.Any(x => x == 1);

            if (!coinsContainOne)
            {
                throw new IndexOutOfRangeException("Coins array must contain coin 1.");
            }

            Array.Sort(coinsAsArray);
            Array.Reverse(coinsAsArray);

            foreach (var item in coinsAsArray)
            {
                if (item > coin)
                {
                    continue;
                }

                return item;
            }

            return 0;
        }

        public static int[] MakeChange(int coin, IEnumerable<int> coins)
        {
            var changeArr = coins.ToArray();
            var list = new List<int>();
            var currentCoin = coin;

            while (currentCoin > 0)
            {
                var currentChange = MinimalChangeForCoin(currentCoin, changeArr);
                list.Add(currentChange);
                currentCoin -= currentChange;
            }

            var result = list.ToArray();

            return result;
        }
    }
}