I have a list box with a bunch of values in it. I also have an UP button and a DOWN button. With these buttons, I would like to move the selected item in the list box up/down. I am having trouble doing this.

Here is my code so far:

    private void btnDataUp_Click(object sender, RoutedEventArgs e)
    {

        int selectedIndex = listBoxDatasetValues.SelectedIndex; //get the selected item in the data list

        if (selectedIndex != -1 && selectedIndex != 0) //if the selected item is selected and not at the top of the list
        {
            //swap items here
            listBoxDatasetValues.SelectedIndex = selectedIndex - 1; //keep the item selected
        }


    }

I do not know how to swap the values! Any help would be GREATLY appreciated!