how to write bulk of code in windows service

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C#

actully i did windows service. only i test when start methord is executed then one file created and writing some text and also for stop methord another methord is creatcued and same. this code perfectly executed.but when i write some bulk of code instead of small code it is not executing .becoz the interval time is low.but when i increase the time interval then it is not install to my computer it show error "after install start methord is not excute" so please comment how to write bulk of code in window service please please...

my time interval is 1000

it is perfectly working in this code

string sfilepath = @"filepath/sample.txt";
string sdatetime = DateTime.Now.ToString();
System.IO.StreamWriter ofilewriter = new System.IO.StreamWriter(sfilepath, true);
ofilewriter.WriteLine("\n" + "Start Excuting");
ofilewriter.Close();


////when i put this code
con.Open();
string str = "select filed from tablename where field= 1 and field= 0";
MySqlCommand cmd = new MySqlCommand(str, con);
MySqlDataReader sdr = cmd.ExecuteReader();
while (sdr.Read())
{
mailaddress = sdr["field"].ToString();
destinationpath = sdr["field"].ToString();
extnid = sdr["field"].ToString();

string path = destinationpath.Replace('@', '\\');
MailMessage mail = new MailMessage();

SmtpClient SmtpServer = new SmtpClient("smtp.gmail.com");

mail.From = new MailAddress("source mail address");
mail.To.Add(destination mail address);
mail.Subject = "Configuration File";
mail.Body = "Report";
Attachment attachment = new Attachment(path);
mail.Attachments.Add(attachment);
SmtpServer.Port = 25;
SmtpServer.Credentials = new System.Net.NetworkCredential("source mail", "passwo0rd");
SmtpServer.EnableSsl = true;

SmtpServer.Send(mail);
MessageBox.Show("message sent");

//update in table message was send.

}
con.Close();

}
it does not work properly,only message sent but no update in table and sometime message is not send like this.



thanks in advance....