C#中字符,字符串的大小写转换

using System;
using System.Globalization;
using System.Threading;

namespace csConsole
{

    public class MyClass 
    {
        public static void Main() 
	{ 
	  string title="this is my converted string";
          Console.WriteLine("String Class");
          Console.WriteLine("------------");
			
          //Convert string to uppercase.
          Console.WriteLine(title.ToUpper());
          //Convert string to lowercase.
          Console.WriteLine(title.ToLower());
	
          Console.WriteLine();
          Console.WriteLine("TextInfo Class");
          Console.WriteLine("--------------");

          //Get the culture property of the thread.
          CultureInfo cultureInfo   = Thread.CurrentThread.CurrentCulture;
          //Create TextInfo object.
          TextInfo textInfo = cultureInfo.TextInfo;
                    
          //Convert to uppercase.
          Console.WriteLine(textInfo.ToUpper(title));
          //Convert to lowercase.
          Console.WriteLine(textInfo.ToLower(title));
          //Convert to title case.
          Console.WriteLine(textInfo.ToTitleCase(title));
	}
    }
}

                char itemLower = char.ToLower(item);
                char itemUpper = char.ToUpper(item);