我无法删除列表框中的索引

Question

I'm trying to remove to selected index in my Listbox but I get an error:

System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection. (Parameter 'index')

Please help me, I'm a newbie to C#.

public void listBoxName_SelectedIndexChanged(object sender, EventArgs e)
{
    int index = listBoxName.SelectedIndex;
    labelName.Text = clients[index].Name;
    labelAge.Text = clients[index].Age.ToString();
    labelPhone.Text = clients[index].Phone;
    labelAddress.Text = clients[index].Address;
}

private void buttonClearFields_Click(object sender, EventArgs e)
{
    textBoxName.Text = "";
    textBoxAge.Text = "";
    textBoxPhone.Text = "";
    textBoxAddress.Text = "";
}

private void buttonRemove_Click(object sender, EventArgs e)
{
    listBoxName.Items.RemoveAt(listBoxName.SelectedIndex);
}

Answer 1

int index = listBoxName.SelectedIndex;
if (index < 0 || index > clients.Length) return;

Answer 2

listBoxName.Items.RemoveAt requires the passed index to be in the range 0..(n-1) , where n is the number of items currently in listBoxName .

It looks like in your case listBoxName.SelectedIndex returns a negative value.

It could be either because listBoxName is empty, or it contains items but none is selected.

A possible fix would be:

private void buttonRemove_Click(object sender, EventArgs e)
{
    int selIdx = listBoxName.SelectedIndex;
    if (selIdx < 0 || selIdx >= listBoxName.Items.Count) return;
    listBoxName.Items.RemoveAt(selIdx);
}