Split by Word Casing/ Lists, Arrays

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




class Program
{
    static void Main(string[] args)
    {
        string[] words = Console.ReadLine()
            .Split(",;:.!()\"'\\/[] ".ToCharArray
            (), StringSplitOptions.RemoveEmptyEntries);

        List<string> upperCase = new List<string>();
        List<string> lowerCase = new List<string>();
        List<string> mixedCase = new List<string>();

        foreach (var word in words)
        {
            if (IsUpperWord(word))
            {
                upperCase.Add(word);
            }
            else if (IsLowerWord(word))
            {
                lowerCase.Add(word);
            }
            else
            {
                mixedCase.Add(word);
            }
        }
        Console.WriteLine("Lower-case: {0}", string.Join(", ", lowerCase));
        Console.WriteLine("Mixed-case: {0}", string.Join(", ", mixedCase));
        Console.WriteLine("Upper-case: {0}", string.Join(", ", upperCase));
    }

    static bool IsUpperWord(string word)
    {
       for (int i = 0; i<word.Length; i++)
        {
            char symbol = word[i];
            if ('A' > symbol || symbol > 'Z')
            {
                return false;
            }
        }
        return true;
    }

    static bool IsLowerWord(string word)
    {
        foreach (char symbol in word)
        {
            if ('a' > symbol || symbol > 'z')
            {
                return false;
            }
        }
        return true;
    }
}