Question

Is there some event I can use to tell when the SelectedIndices property changes for a listbox? I want to deselect items in a listbox based on a certain property value of the item. I’ve hooked up an event that works for when a SelectedIndex is changed, but not sure how to do it for when the SelectedIndices property changes for multiselection.

private void listBox1_SelectedIndexChanged(object sender, EventArgs e)
{
     Curve curItem = (Curve)listBox1.SelectedItem;
     int index = listBox1.Items.IndexOf(curItem);

     if (curItem.newName == null)
     {
          listBox1.SetSelected(index, false);
     }
}

Answer 1

According to MSDN, this event will be fired every time the selection changes:

If the SelectionMode property is set to SelectionMode.MultiSimple or SelectionMode.MultiExtended, any change to the SelectedIndices collection, including removing an item from the selection, will raise this event.

So basically, you can use it the same way as using it with single selection.

Sample:

For example if you want to deselect all items with null as newName:

foreach (var item in listBox1.SelectedItems)
{
    if ((item as Curve).newName == null)
    {
        int index = listBox1.SelectedItems.IndexOf(item);
        listBox1.SetSelected(index, false);
    }
}

(I’m not sure if you can deselect items inside a foreach loop since it changes the SelectedItems object itself. If it does not work, you can still make a temporary list of those items and deselect them after the loop.)