以下是引用lyy3146在2010-8-31 16:08:08的发言：

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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            char c1= 'a';
            char c2 = 'b';
            char c3 = 'C';
            char c4 = '4';
            if (char.IsLower(c1) ||
                char.IsLower(c2) ||
                char.IsLower(c3) ||
                char.IsLower(c4))
            {
                Console.WriteLine("A char is lowercase");
            }
            if (char.IsUpper(c1) ||
                char.IsUpper(c2) ||
                char.IsUpper(c3) ||
                char.IsUpper(c4))
            {
                Console.WriteLine("A char is Uppun");
            }
            String sample = "UPPERCASE WORD";
            Console.WriteLine(sample.ToLower());
            Console.ReadLine();   




        }
    }
}