Google I/O 2012 Redirect Checker

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net;
using System.IO;
using System.Threading;
using Microsoft.Office.Interop.Outlook;
using System.Text.RegularExpressions;

namespace GoogleIOAlert
{
    class Program
    {
        private const string url = "http://www.google.com/io";
        private const string urlRedirect = "http://www.google.com/events/io/2011/index-live.html";
        private const string userAgent = "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/535.11 (KHTML, like Gecko) Chrome/17.0.963.56 Safari/535.11";
        private const int minBackoffTime = 10;               //5 seconds
        private const string emailSubject = "Google I/O 2012 Site Updated";
        private const string emailBody = "Quick, go to " + url + "\n Maybe they opened registration!";

        private const string emailRegex = @"^(?("")(""[^""]+?""@)|(([0-9a-z]((\.(?!\.))|[-!#\$%&'\*\+/=\?\^`\{\}\|~\w])*)(?<=[0-9a-z])@))" +
        @"(?(\[)(\[(\d{1,3}\.){3}\d{1,3}\])|(([0-9a-z][-\w]*[0-9a-z]*\.)+[a-z0-9]{2,17}))$";

        private static HttpWebRequest currentRequest;
        private static HttpWebResponse currentResponse;
        private static StringBuilder output;
        private static int backoffTime = minBackoffTime;
        private static string emailAddress;

        static void Main(string[] args)
        {
            //Get user email address
            Console.Write("Enter a valid email address to which you would like me to alert: ");
            emailAddress = Console.ReadLine();

            //Validate email address
            while (!Regex.IsMatch(emailAddress, emailRegex, RegexOptions.IgnoreCase))
            {
                //Get user email address
                Console.Write("Invalid email address, try again: ");
                emailAddress = Console.ReadLine();
            }

            Console.WriteLine("An email will be sent to " + emailAddress + " as soon as the redirect changes for " + url + "\n");

            int attemptNumber = 1;

            //Listen for changes
            while (true)
            {
                //Set request timeout and user agent
                currentRequest = (HttpWebRequest) HttpWebRequest.Create(url);
                currentRequest.Timeout = backoffTime * 1000;
                currentRequest.UserAgent = userAgent;

                output = new StringBuilder();
                output.Append("Attempt #");
                output.Append(attemptNumber++);
                output.Append(":\n");
                output.Append("Fetching Google IO...\n");

                Console.WriteLine(output.ToString());
                output.Clear();

                try
                {
                    currentResponse = (HttpWebResponse)currentRequest.GetResponse();
                    output.Append("Response URI: ");
                    output.Append(currentResponse.ResponseUri.ToString());
                    output.Append("\n");

                    if (!urlRedirect.Equals(currentResponse.ResponseUri.ToString()))
                    {
                        //If the url redirect has changed
                        output.Append("The Google IO 2012 Site is up!\n");
                        Microsoft.Office.Interop.Outlook.Application oApp = new Microsoft.Office.Interop.Outlook.Application();
                        MailItem newEmail = (Microsoft.Office.Interop.Outlook.MailItem)oApp.CreateItem(Microsoft.Office.Interop.Outlook.OlItemType.olMailItem);
                        newEmail.Recipients.Add(emailAddress);
                        newEmail.Subject = emailSubject;
                        newEmail.Body = emailBody;
                        newEmail.Send();

                        Console.WriteLine(output.ToString());
                        output.Clear();

                        break;
                    }
                    else
                    {
                        output.Append("Nothing has changed yet.\n");
                    }

                    currentResponse.Close();

                    output.Append(url);
                    output.Append(" request successful.");

                    if (backoffTime != Math.Max(minBackoffTime, (int)((float)backoffTime * (2.0f / 3.0f))))
                    {
                        //If the backoff time can be reduced
                        output.Append(" Decreasing backoff time from ");
                        output.Append(backoffTime);
                        output.Append(" seconds to ");

                        backoffTime = Math.Max(minBackoffTime, (int)((float)backoffTime * (2.0f / 3.0f)));

                        output.Append(backoffTime);
                        output.Append(" seconds.");
                    }

                    output.Append("\n");
                }
                catch (WebException e)
                {
                    if (e.Status == WebExceptionStatus.Timeout)
                    {
                        //Backoff a bit
                        output.Append(url);
                        output.Append(" timed out. Increasing backoff time from ");
                        output.Append(backoffTime);
                        output.Append(" seconds to ");

                        backoffTime = (int)Math.Ceiling(backoffTime * 1.5);

                        output.Append(backoffTime);
                    }
                    else
                    {
                        output.Append("Web exception: ");
                        output.Append(e.Message);
                    }

                    output.Append("\n");
                }
                finally
                {
                    output.Append("Waiting ");
                    output.Append(backoffTime);
                    output.Append(" seconds until next request.\n\n");

                    Console.Write(output.ToString());
                    output.Clear();
                    Thread.Sleep(backoffTime * 1000);
                }

            }
            Console.WriteLine("Program ended.");
            Console.WriteLine("Press any key to exit.");
            Console.ReadKey();
        }
    }
}