C#转换字符大小写

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

namespace Demo {
   class MyApplication {
      static void Main(string[] args) {

         string str;
         str = "AMIT";
         Console.WriteLine("UpperCase : {0}", str);

         // convert to lowercase
         Console.WriteLine("Converted to LowerCase : {0}", str.ToLower());
         Console.ReadLine();
      }
   }
}