Begin Invoke/Exceptions - Thread Life

Hi,

I am writing an app that uses code similar to the below...

The code updates a label as "loading..." while invoking the method doSomething().

If the user closes the window in the app that has kicked off this operation, then thread is still alive. In the code below I simulate an exception occuring and this displays a text box.

 Obviously if the user clicks the close button, they will not want to see the error message as they would believe the method was cancelled. Is there any good approaches for this kidna of scenario?

I can call thread.abort in the closing window method and this does the job, but this means I need a global thread variable in my class.

I'm curious if there is a better way to do this, any help is very much appreciated.

 private void btn_Click(object sender, RoutedEventArgs e)
        {
            ThreadStart ts = new ThreadStart(worker);
            Thread t = new Thread(ts);
            t.IsBackground = true;
            t.Start();
        }
        public void worker()
        {
            Action mydel = new Action(doSomething);
            IAsyncResult result = mydel.BeginInvoke(null, null);
            int i = 0;
            string message = "Loading";
            while (!(result.IsCompleted))
            {
                myLabel.Dispatcher.Invoke(
               System.Windows.Threading.DispatcherPriority.Normal,
               new Action(
                 delegate()
                 {
                     if (i < 8)
                     {
                         myLabel.Content = myLabel.Content + ".";
                         i++;
                     }
                     else
                     {
                         myLabel.Content = message;
                         i = 0;
                     }
                 }
                 ));
                Thread.Sleep(500);
            }
            try
            {
                mydel.EndInvoke(result);
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }
        public void doSomething()
        {
            Thread.Sleep(10000);
            throw new Exception();
        }