how to collect datagriedviewchekbox selected value in array

protected void btnClick_Click(object sender, EventArgs e)
{ 
	foreach (DataGridViewRow row in dataGridView1.Rows)
        {
           DataGridViewCheckBoxCell chk = row.Cells[0] as DataGridViewCheckBoxCell;

           if (Convert.ToBoolean(chk.Value) == true)
		{
                    //Add code here for adding into array
		}

        }

}