private void ToggleCategorySelection(Category category)
 {
     MultiselectItem container = categoriesListBox.ItemContainerGenerator.ContainerFromItem(category) as MultiselectItem;
     if (null != container)
     {
         container.IsSelected = !container.IsSelected;
     }
 }
 private void selectItemOnPageLoaded(Category category)
 {
     MultiselectItem container = categoriesListBox.ItemContainerGenerator.ContainerFromItem(category) as MultiselectItem;
     if (null != container)
     {
         container.IsSelected = !container.IsSelected;
     }
     else
     {
         //on long list the container could be null since the list is not fully rendered on the screen, so we can't select items at the end of the list
         categoriesListBox.SelectedItems.Add(category);
     }
 }