C#

public delegate void ThreadCompleterEventHandler(object sender, ThreadCompleteEventArgs args);

public class ObjectThatCreatesAThread
{
    public event ThreadCompleterEventHandler ThreadCompleted;
    private Thread t;

    public ObservableCollection<string> StringsCollection;

    public ObjectThatCreatesAThread()
    {
        StringsCollection = new ObservableCollection<string>();
    }

    public void PopulateStringsCollectionOnOtherThread()
    {
        t = new Thread(delegate()
            {
                DoWork();
            });
        t.Name = "Populate StringsCollection Thread";
        t.Start();
    }

    private void DoWork()
    {
        StringsCollection.Add("String1");
        StringsCollection.Add("String2");
        StringsCollection.Add("String3");
        OnThreadCompleted();
    }

    private void OnThreadCompleted()
    {
        ThreadCompleted(this, new ThreadCompleteEventArgs());
    }
}

private void RunThread_Click(object sender, RoutedEventArgs e)
{
    obj = new ObjectThatCreatesAThread();
    obj.ThreadCompleted += new ThreadCompleterEventHandler(obj_ThreadCompleted);
    obj.PopulateStringsCollectionOnOtherThread();
}

void obj_ThreadCompleted(object sender, ThreadCompleteEventArgs args)
{
    StringsListBox.ItemsSource = obj.StringsCollection;
}

void obj_ThreadCompleted(object sender, ThreadCompleteEventArgs args)
{
    Dispatcher.BeginInvoke(DispatcherPriority.Normal, new Action(delegate()
    {
        StringsListBox.ItemsSource = obj.StringsCollection;
    }));
}