百思不得骑姐的问题——难道是控件的bug？

 private void clbSaleDept_SelectedIndexChanged(object sender, EventArgs e)
        {
            CheckedListBox cb = sender as CheckedListBox;

            if (cb == null || cb.SelectedIndex < 0)
            {
                return;
            }
            //如果单击“全选”
            if (cb.SelectedIndex == 0)
            {
                for (int i = 1; i < cb.Items.Count; i++)
                {
                    Console.WriteLine(cb.GetItemChecked(0));
                    cb.SetItemChecked(i, cb.GetItemChecked(0));
                }
            }
            else
            {
                if (!cb.GetItemChecked(cb.SelectedIndex))
                {//当其它选项有一项未选中，则取消“全选”
                    cb.SetItemChecked(0, false);
                }
                else if (!cb.GetItemChecked(0) && cb.SelectedItems.Count >= (cb.Items.Count - 1))
                {//当其它所有选中，则选中“全选”
                    cb.SetItemChecked(0, true);
                }
            }
        }