C#

// Create a Timer with a Normal Priority
DispatcherTimer _timer = new DispatcherTimer(DispatcherPriority.Normal);

// Set the Interval to 2 seconds
_timer.Interval = TimeSpan.FromMilliseconds(2000);

// Set the callback to just show the time ticking away
// NOTE: We are using a control so this has to run on
// the UI thread
_timer.Tick += new EventHandler(delegate(object s, EventArgs a)
{
    UpdateWeather();
});

// Start the timer
_timer.Start();

backgroundMessageGetter.DoWork += new DoWorkEventHandler(backgroundMessageGetter_DoWork);
backgroundMessageGetter.RunWorkerCompleted += new RunWorkerCompletedEventHandler(backgroundMessageGetter_RunWorkerCompleted);
backgroundMessageGetter.ProgressChanged += new ProgressChangedEventHandler(backgroundMessageGetter_ProgressChanged);
backgroundMessageGetter.WorkerReportsProgress = true;
backgroundMessageGetter.RunWorkerAsync(this);

void backgroundMessageGetter_DoWork(object sender, DoWorkEventArgs e)
{
    try
    {
        while (true)
        {
            GlobalWeatherService.GlobalWeatherSoapClient proxy = new aXYZ.GlobalWeatherService.GlobalWeatherSoapClient("GlobalWeatherSoap12",
                "http://www.webservicex.net/globalweather.asmx");

            string weatherXml = proxy.GetWeather("Port Elizabeth", "South Africa");
            //some other processing

            backgroundMessageGetter.ReportProgress(0);
            Thread.Sleep(2000);
        }
    }
    catch (Exception error)
    {
        System.Windows.MessageBox.Show(error.Message);
    }
}

void backgroundMessageGetter_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
    //update UI
}