checkedListBox

private void button3_Click(object sender, EventArgs e)
{
for (int i = 0; i < checkedListBox1.Items.Count; i++)
{
if (checkedListBox1.GetItemChecked(i))
{
checkedListBox1.Items.RemoveAt(i);
i--;
}
}

private void button11_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);
}
}
}