在datagridview中如何将2列冻结？

private void Form1_Load(object sender, EventArgs e)
{
    dataGridView1.Columns[0].Frozen = true;
    dataGridView1.Columns[1].Frozen = true;
}

private void button1_Click(object sender, EventArgs e)
{
    dataGridView1.Columns[0].Frozen = !dataGridView1.Columns[0].Frozen;
    dataGridView1.Columns[1].Frozen = !dataGridView1.Columns[1].Frozen;
}