How to count and compare number in datagirdview C#

public void BtnSearch_Click(object sender, EventArgs e)

       {
           db = new DbConnector();
           lbTotal.Text = "00";

           db.fillDataGridView("select *from tbl_WorkLoad where TimeComplete Between'" + dateTimePicker1.Value.ToString("dd-MM-yy| HH:mm:tt") + "' and '" + dateTimePicker2.Value.ToString("dd-MM-yy| HH:mm:tt") + "'", dataGridView1);

           const string HardWorkLabelText = "Hard Work Count: {0}";
           const int HardWorkThreshold = 30;

           try
           {
               IEnumerable<DataGridViewRow> rows = dataGridView1.Rows.Cast<DataGridViewRow>().Where(r => ((Int32)r.Cells["TotalTime"].Value) >= HardWorkThreshold);

               lbHardwork.Text = string.Format(HardWorkLabelText, rows.Count());

               {
                   for (int i = 0; i < dataGridView1.Rows.Count; i++)
                   {
                       lbTotaltime.Text = (Convert.ToString(double.Parse(lbTotaltime.Text) + double.Parse(dataGridView1.Rows[i].Cells[7].Value.ToString())));

                  
           }
           catch (Exception ex)
           {

               MessageBox.Show(ex.Message.ToString());
           }
       }