Getting "UnauthorizedAccessException" in BackgroundWorker without access to UI thread

Question

I do the hard work with the background so that this does not affect my Silverlight UI thread. However, in the DoWork function, I get this exception:

UnauthorizedAccessException "Invalid access to multiple threads."

I know that I cannot access the user interface stream from BackgroundWorker. However, this exception occurs on this line:

  ListBoxItem insert = new ListBoxItem();

How is this access to my u thread?

Here's the actual piece of code I narrowed it down. I basically do the job by creating listboxitems that I would like to insert into the list sourceList:

void FillSourceList()
{
    busyIndicator.IsBusy = true;
    BackgroundWorker bw = new BackgroundWorker();
    bw.DoWork += (sender, args) =>
        {
            List<ListBoxItem> x = new List<ListBoxItem>();
            for (int i = 0; i < 25; i++ )
            {
                ListBoxItem insert = new ListBoxItem(); //<---Getting exception here
                insert.Content = "whatever";
                x.Add(insert);
            }
            args.Result = x;
        };
    bw.RunWorkerCompleted += (sender, args) =>
        {
            foreach (ListBoxItem insert in (List<ListBoxItem>)(args.Result))
                sourceList.Items.Add(insert);
            busyIndicator.IsBusy = false;
        };

    bw.RunWorkerAsync();
}

Answer 1

A ListBoxitem Control, GUI. , "" , , , .

: x () Completed.