winform CheckedListBox实现全选/全不选

/全选
        private void button3_Click(object sender, EventArgs e)
        {
            for (int i = 0; i < this.checkedListBox1.Items.Count; i++)
            {
                this.checkedListBox1.SetItemChecked(i, true);
            }

}
        //反选
        private void button4_Click(object sender, EventArgs e)
        {
            for (int i = 0; i < checkedListBox1.Items.Count; i++)
            {
                if (checkedListBox1.GetItemChecked(i))
                {
                    checkedListBox1.SetItemChecked(i, false);
                }
                else
                {
                    checkedListBox1.SetItemChecked(i, true);
                }
            }
        }