How can i set checked and uncheck checkbox column in Gridvie

private void chkbox_CheckedChanged(object sender, EventArgs e)
 {
 foreach (DataGridViewRow row in dataGridView1.Rows)
{
 DataGridViewCheckBoxCell chk = (DataGridViewCheckBoxCell)row.Cells[1];

// set cell index of your checkbox position in datagrid
 if (chk.Value == chk.TrueValue)
{
chk.Value = chk.FalseValue;
}
 else
 {
 chk.Value = chk.TrueValue;
}
}
 }