Collection was modified; enumeration may not execute error when removing a ListItem from a LIstBox

Question

I have two ListBoxes, lstAvailableColors and lstSelectedColors. Between each listbox are two buttons, Add and Remove. When a color or colors is selected in lstAvailableCol

Answer 1

Maybe this is what you need

protected void btnAdd_Click(object sender, EventArgs e)
{
    while(listBox1.SelectedIndex!=-1)
    {
           listBox1.Items.Remove(listBox1.SelectedItem);
    }
}