Last Digit Of an Integer Number As English Word

using System;

class LastDigitOfIntAsEnglishWord
{
  static string DigitAsEnglishWord(string digit)
  {
    string lastDigit = digit.Substring(digit.Length-1, 1);//Get the last symbol in the string by making a sustring from the last position

    switch (lastDigit)//Switch the cases
    {
      case "0": { digit = "zero"; } break;
      case "1": { digit = "one"; } break;
      case "2": { digit = "two"; } break;
      case "3": { digit = "three"; } break;
      case "4": { digit = "four"; } break;
      case "5": { digit = "five"; } break;
      case "6": { digit = "six"; } break;
      case "7": { digit = "seven"; } break;
      case "8": { digit = "eight"; } break;
      case "9": { digit = "nine"; } break;
      default: { digit = "Not a digit!"; } break;//If the symbol isn't a digit, print a warning.
    }
    return digit;
  }
  static void Main()
  {
    Console.Write("Please enter an integer number:");
    string inputNum = Console.ReadLine();

    string result = DigitAsEnglishWord(inputNum);
    Console.WriteLine(result);
  }
}