Generate Letters - Alphabet

        static char[] GenerateLetters(bool upperCase = false)
        {
            int aint = (int)'a';
            char[] letters = new char[26];
            for (int i = 0; i < letters.Length; i++)
            {
                char letter = (char)aint++;
                letters[i] = upperCase ? char.ToUpper(letter) : letter;
            }
            return letters;
        }