ListBox.Items和ListBox.SelectedItems是否已链接？

Question

I'm working on a WinForms project, on which there is a TextBox where the user can input a search query, and a ListBox where all items are visible and matched items highlighted.

When I'm iterating through ListBox.Items and modifying ListBox.SelectedItems , I get an InvalidOperationException: List that this enumerator is bound to has been modified. An enumerator can only be used if the list does not change. InvalidOperationException: List that this enumerator is bound to has been modified. An enumerator can only be used if the list does not change.

Here's the code

private void SearchTextBox_TextChanged(object sender, EventArgs e)
{
    listBox.ClearSelected();

    foreach (var item in listBox.Items) // Exception happens here...
    {
        if (item.ToString().Contains(SearchTextBox.Text))
            listBox.SelectedItems.Add(item); // ... but I'm not modifying listBox.Items
    }
}

I've already thought of a better solution, but I would still like to know why the exception happened.

Is there some kind of link between ListBox.Items and ListBox.SelectedItems , or why does modifying one, make enumerating through the other impossible?

Answer 1

Per MSDN ListBox.Items , you would want to add items through the following code:

listbox.Items.Add();

EDIT: (I meant to add the following after rereading the ? but my laptop turned off due to low battery)

   listBox1.SetSelected(<index>, true);
   listBox1.SetSelected(<index>, true);
   listBox1.SetSelected(<index>, true);

Answer 2

Items are not just the objects in the ListBox but also its state like the selected state. So you need to use a loop without an Enumerator to change the state of an item regardless of the way you change the state. Makes no difference if you use SelectedItems, SelectedIndices, SetSelected or whatever.