Nine-Digit Magic Numbers

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

namespace NineDigitMagicNumbers
{
    class Program
    {
        static void Main(string[] args)
        {
            // input
            int sum = int.Parse(Console.ReadLine());
            int diff = int.Parse(Console.ReadLine());

            // declarations
            IEnumerable<string> combinations = CombinationsWithRepition("1234567", 3);
            List<string> workCopy = combinations.ToList();
            List<int> numbers = workCopy.Select(int.Parse).ToList();
            List<int> result = new List<int>();

            for (int i = 0; i < numbers.Count; i++)
            {
                for (int j = i + 1; j < numbers.Count; j++)
                {
                    for (int k = j + 1; k < numbers.Count; k++)
                    {
                        string temp1 = workCopy[i] + workCopy[j] + workCopy[k];
                        int temp2 = int.Parse(temp1);
                        int tempSum = 0;
                        for (int l = 1; l <= 9; l++)
                        {
                            tempSum += GetDigit(temp2, l);
                        }

                        if (tempSum == sum && (numbers[k] - numbers[j] == diff) && (numbers[j] - numbers[i] == diff))
                        {
                            result.Add(temp2);
                        }
                    }
                }
            }

            if (result.Count > 0)
            {
                foreach (var item in result)
                {
                    Console.WriteLine(item);
                }
            }
            else
            {
                Console.WriteLine("No");
            }
        }
        static String Convert(string symbols, int number, int totalLen)
        {
            var result = "";
            var len = symbols.Length;
            var nullSym = symbols[0];
            while (number > 0)
            {
                var index = number % len;
                number = number / len;
                result = symbols[index] + result;
            }
            return result.PadLeft(totalLen, nullSym);
        }

        static IEnumerable<String> CombinationsWithRepition(string symbols, int len)
        {
            for (var i = 0; i < Math.Pow(symbols.Length, len); i++)
                yield return Convert(symbols, i, len);
        }

        static int GetDigit(int number, int digit)
        {
            return (number / (int)Math.Pow(10, digit - 1)) % 10;
        }
    }
}