Checkbox want to be checked in datagridview

private void dataGridView1_CellContentClick(object sender, DataGridViewCellEventArgs e)
{
if (e.ColumnIndex == 1)
{
	if (DataGridView1.Rows[e.RowIndex].Cells[1].Value == null || DataGridView1.Rows[e.RowIndex].Cells[1].Value == DBNull.Value || Convert.ToBoolean(DataGridView1.Rows[e.RowIndex].Cells[1].Value) == false)
	{
  	   DataGridView1.Rows[e.RowIndex].Cells[1].Value = true;
	}
 }
}