Issue with auto check of Checkbox in LonglistSector

I'm working with LonglistSector, and i got problem like this guy, link: Why does WP8 LongListSelector incorrectly re-use Checked state of CheckBox?. I read Dennis's answer, i understand problem, but i dont known how to did it, i try using VisualTreeHelper for get checkbox checked, my code example:

private string SearchVisualTree(DependencyObject targetElement)
        {
            var count = VisualTreeHelper.GetChildrenCount(targetElement);
            for (int i = 0; i < count; i++)
            {
                var child = VisualTreeHelper.GetChild(targetElement, i);
                if (child is CheckBox)
                {
                    CheckBox targetItem = (CheckBox)child;

                    if (targetItem.IsChecked == true && targetItem.IsPressed==true)
                    {
                        result = targetItem.Tag.ToString();
                        break;
                    }
                }
                else
                {
                    SearchVisualTree(child);
                }
            }
            return result;
        }

I got the result:

 idBH = SearchVisualTree(Longlistsector);

I got the Checkbox.Tag, but other checkbox still checked ! How can I fix this, need help.....