SelectedIndexChanged not fired by bound listbox when starting deleting first entries

stefan posted on Wednesday, April 04, 2007

Hi,

I have a Listbox bound to a BusinessListBase through a bindingsource.
There is a button near, that enables the user to delete items from the BusinessListBase.

        private void btnDeleteCriteria_Click(object sender, EventArgs e)
        {
            if (_currentCrit != null) _query.criteria.Remove(_currentCrit);
        }

The _currentCrit child reference is set in the listbox' SelectedIndexChanged event handler.
The listbox behaves as expected when I choose to delete the last entry from the list.
The selected entry is deleted from the list, and thanks to the SelectedIndexChanged event firing, 
_currentCrit is set to the next (= previous) item in the list, so the user could go on deleting from the list.

As soon as I want to delete an item that's not the last in the list, SelectedIndexChanged is not
fired, although the listbox apparently seems to select the next (= next in line) item, which is not
the case. My reference is still set to the previously deleted object.

What am I doing wrong here?

As I wrote this, I realized that actually the index of the selected item is never going to change
when not deleting the last position....dumb me.
Is there any chance of getting a 'SelectedItemChanged' equivalent for the listbox control?

Stefan

Bayu replied on Wednesday, April 04, 2007

Why don't you replace your _currentCrit reference with an _currentIndex variable?

;-)

Bayu

stefan replied on Wednesday, April 04, 2007

Hi Bayu!

Relying on the index doesn't sound as a goog idea to me, because the index of an object could
change. I feel better having an extra reference to the current object, as I need it to hook and unhook
PropertyChanged event handlers on it.

Anyway, I solved my issue by coding the following check for "-1":
private void btnDeleteCriteria_Click(object sender, EventArgs e)
{
 if (_currentCrit != null) _query.criteria.Remove(_currentCrit);
 // when not deleting the last item in the list, _currentCrit is not reset automatically
 // to the current listselection, because 'SelectedIndexChanged' did not fire,
 // and _currentCrit still points to the deleted object!
 if (criteriaListBox.Items.IndexOf(_currentCrit) == -1)
 {
  UserQueryCriteria _selectedCrit = criteriaListBox.SelectedItem as UserQueryCriteria;
  if (_selectedCrit != null) UpdateCriteriaEditArea(_selectedCrit);
 }
}

Thanks for your support!

Stefan