Palindrome checker

Palindrome

using System;
using System.IO;
using System.Text;

namespace PalindromeChecker
{
    public class Program
    {
        public static void Main(string[] args)
        {
            using(StreamReader sr = new StreamReader("palindrome.in"))
            {
                string num = sr.ReadLine();
                int numberOfInputs = Int32.Parse(num);
                
                string line;
                int count = 1;
                bool isFirstLine = true;
                
                while ((line = sr.ReadLine()) != null && 
                    (count <= numberOfInputs)) {
                                            
                    using (StreamWriter sw = File.AppendText("palindrome.out")) {
                        sw.WriteLine("Case #{0}", count);
                        
                        if (isPalindrome(line)) {
                            sw.WriteLine("yes");
                        } else {
                             sw.WriteLine("no");
                        }
                    }
                    
                    count++;
                }
            }
            
            Console.WriteLine("Done");
        }
        
        static bool isPalindrome(String s) {
            if (String.IsNullOrEmpty(s)) {
                return true;
            }
            
            int start = 0;
            int end = s.Length - 1;
            
            while (start < end) {
                if (s[start] != s[end]) {
                    return false;
                }
                start++;
                end--;
            }
            
            return true;
        }
    }
}