Question

This works fine:

private void btnDelete_Click(object sender, EventArgs e)
{
    for (int i = 0; i < listBox1.SelectedItems.Count; i++) 
    {
        listBox1.Items.Remove(listBox1.SelectedItems[i].ToString());
        i--;
    }
}

But this doesn’t work:

private void btnDelete_Click(object sender, EventArgs e)
{
    listBox1.Items.Remove(listBox1.SelectedItems);
}

Why is the second btnDelete_Click not working? I mean I select a line on my listBox1 with my mouse and then press the button.
Doesn’t the .Remove function recognize which line I selected? Even though I say .Remove(listBox1.SelectedItem), is it a must to have and selectedItem array? Isn’t the word SelectedItems self-explanatory? And since I clicked the line on my listBox1 with my mouse, can’t the program or the IDE understand which line is selected? Why do I still have to use SelectedItems[i]?

Answer 1

The reason the second example does not work is because you are trying to pass multiple items in the form of a collection to be removed at once.

To remove an item you need to do it one at a time, hence why you need a loop.

Also, might I suggest using a ListView instead? I personally find them easier to use with many more options.

For example you could make your loop for a ListView with just this

foreach (ListViewItem item in listView1.SelectedItems)
{
    item.Remove();
}

If you are trying to remove only one item at a time that is selected then you do

listBox1.Items.Remove(listBox1.SelectedItem);

SelectedItem rather than SelectedItems, plural being the collection that it can’t handle without a loop, singular being a single item that it can understand.