write code into saperate file

public partial class Service1 : ServiceBase
    {

        public string AppPath = Directory.GetParent(Directory.GetParent(Directory.GetCurrentDirectory()).ToString()).ToString();
        Timer timer = new Timer();
        Voucher vocher;
        private DataSet ds;

        public Service1()
        {
            InitializeComponent();
        }

        protected override void OnStart(string[] args)
        {
            //WebServiceMethod("start service");
            WebServiceMethod();
            //handle Elapsed event
            timer.Elapsed += new ElapsedEventHandler(OnElapsedTime);
            //This statement is used to set interval to 5 minute (= 3,00,000 milliseconds)
            timer.Interval = 300000;
            //enabling the timer
            timer.Enabled = true;
        }

        private void OnElapsedTime(object source, ElapsedEventArgs e)
        {
            //WebServiceMethod("Another entry at " + DateTime.Now);
            WebServiceMethod();
        }

        protected override void OnStop()
        {
            timer.Enabled = false;
            //WebServiceMethod("stopping service");
            WebServiceMethod();
        }

        private void WebServiceMethod(string content = "")
        {
            WebServiceProxyMethod();

        }


        internal void WebServiceProxyMethod()
        {
            try
            {
                vocher = new Voucher();
                vocher.Credentials = new System.Net.NetworkCredential("000", "000");
                XmlNode xmlnode = vocher.VoucherExport();

                XmlReader xmlReader = new XmlNodeReader(xmlnode);
                using (ds = new DataSet())
                {
                    ds.ReadXml(xmlReader);
                    DataTable dt = ds.Tables["TableName"];
                    if (dt != null)
                    {
                        foreach (DataRow dr in dt.Rows)
                        {
                        }
                    }
                }
            }
            catch (SoapException ex)
            {
                ErrorLog(ex.Message, ex.StackTrace);
            }
            catch (Exception ex)
            {
                ErrorLog(ex.Message, ex.StackTrace);
            }
        }