System.Timers virker ikke i web-service?

Jeg har lavet denne kode:

using System;
using System.Web;
using System.Web.Services;
using System.Web.Services.Protocols;
using System.Timers;

[WebService(Namespace = "http://services/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
public class Service : System.Web.Services.WebService
{
    private Timer controlInterval = new Timer(1000);
    private static int i = 0;

    public Service () {
       
    }

   

    [WebMethod]
    public String runBackUpService(){
        controlInterval.Interval = 500;
        controlInterval.Enabled = true;
        controlInterval.BeginInit();
        controlInterval.Elapsed += new ElapsedEventHandler(controlInterval_Elapsed);
        controlInterval.Start();
        return "Running";
    }

    private static String UpdateBackup()
    {
        i++;
        return "Service has elapsed: " + i + " times";
    }

    private static void controlInterval_Elapsed(object sender, ElapsedEventArgs e)
    {
        UpdateBackup();
    }
}


Jeg forsøger blot at få servicen til at opdatere teksten, hvorfor virker det ikke??? :'(