Question

A ListBox control has an Items property of type ListItemCollection.

I sort of understand why I can’t write

foreach (var item in ShipperListBox.Items)
{
    if (item.Selected) count++;
}

But instead have to write

foreach (ListItem item in ShipperListBox.Items)
{
    if (item.Selected) count++;
}

It has to do with ListItemCollection implementing IEnumerable and not IEnumerable<ListItem> (as explained in this question).

But what I don’t get is why the following is no problem.

for (int i = 0; i < ListBox1.Items.Count; i++)
{
    if (ListBox1.Items[i].Selected) count++;
}

What part of ListItemCollection is making it clear to the compiler that ListBox.Items[i] is of type ListItem?

Answer 1

Because ListItemCollection implements an indexer that returns a ListItem.

This is separate from IEnumerable.