Managed Palindrome C# Solution -- Code

 using System; 
 namespace Palindrome
 {
       /// <summary>
       /// Summary description for PalindromeString.
       /// </summary>
       public class PalindromeString
       {
             static char[] _firstHalf      = null;
             static char[] _secondHalf     = null;
  
             static string _stringToTest = null;
             static int _halfwayMark       = 0;
  
             static PalindromeString() {}
  
             static public bool isPalindrome(string stringToTest, ref int numberOfIters)
             {
                   ++numberOfIters;
  
                   if (_stringToTest != stringToTest)
                   {
                         _stringToTest = stringToTest;
                         char[] stringChars = stringToTest.ToCharArray();
  
                         foreach (char character in stringChars)
                         {
                               if (!char.IsLetterOrDigit(character))
                               {
                                     stringToTest = stringToTest.Replace(character.ToString(), "").ToLower();
                               }
                         }
  
                         _halfwayMark      = (stringToTest.Length/2);
                         _firstHalf        = stringToTest.Substring(0, _halfwayMark).ToCharArray();
                         _secondHalf       = stringToTest.Substring(_halfwayMark).ToCharArray();
  
                         Array.Reverse(_secondHalf);
                   }
  
                   for (int i=0; i < _halfwayMark; i++)
                   {
                         if (_firstHalf[i] != _secondHalf[i])
                         {
                               return false;
                         }
                   }
                   return true;
             }
       }
 }
  
 // harness code :: tests PalindromeString class
  
 using System;
 using System.Collections;
 using System.Text;
 using System.Configuration;
  
 namespace Palindrome
 {
       /// <summary>
       /// Summary description for Class1.
       /// </summary>
       class Class1
       {
             /// <summary>
             /// The main entry point for the application.
             /// </summary>
  
             [STAThread]
             static void Main(string[] args)
             {
                   string testString = "A man, a plan, a canal...Panama!";
                   int numberOfLoops = 0;
                   int iterations = 0;
  
                   // timer vars
                   int start, end;
  
                   // bools
                   bool palindrome = false;
                  
                   Console.Write("Use canned palindrome? y/n ");
                   if (Console.ReadLine().ToUpper() == "Y")
                   {
                         Console.WriteLine("\nText to test: {0}", testString);
                   }
                   else
                   {
                         Console.Write("\nText to test: ");
                         testString = Console.ReadLine();
                   }
  
                   if (PalindromeString.isPalindrome(testString, ref iterations))
                   {
                         Console.Write("\nText IS a Palindrome.  Number of iterations? ");
                         numberOfLoops = Convert.ToInt32(Console.ReadLine());
  
                         // start the counter
                         start = Environment.TickCount;
  
                         Console.WriteLine("\nRunning {0} iterations ", numberOfLoops);
  
                         for (int i=0;i<numberOfLoops;i++)
                         {
                               palindrome = PalindromeString.isPalindrome(testString, ref iterations);
                         }
                         end = Environment.TickCount - start;
                         Console.Write("\nOperation took {0} milliseconds for {1} iterations. ", end.ToString(), iterations.ToString());
                   }
                   else
                   {
                         Console.WriteLine("Text is NOT a Palindrome");
                   }
  
                   Console.Write("\n\nWould you like to try another?  y/n ");
                   if (Console.ReadLine().ToUpper() == "Y")
                   {
                         Main(null);
                   }
                   else
                   {
                         Console.WriteLine();
                   }
             }
     }
 }