check box in datagridview

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C#

Hi there ,
I want to insert value which I select from datagridview ,I have taken check box in datagridview.When i am selecting the value i am getting string ,but i want its value in int.my code is

foreach (DataGridViewRow row in dtstudent.Rows)
               {
                   getbatchid();
                   DataGridViewCheckBoxCell cell = row.Cells["PRESENT"] as DataGridViewCheckBoxCell;
                   ClsConnection.Conn.Close();
                   if (cell.Value != null)
                   {
                       //MessageBox.Show(row.Cells[0].Value.ToString());
                       string s = row.Cells[0].Value.ToString();

                       string str11 = "";
                       string bat_date = dateTimePicker1.Value.ToString("dd/MM/yyyy");
                       str11 = "insert into tbbatch_att(batch_id,student_id,staff_id,attendance_date)values(" + batchid + "," + s + "," + staffid + ",'" + bat_date + "')";

                       SqlCommand cmd11 = new SqlCommand(str11, ClsConnection.Conn);
                       ClsConnection.Conn.Open();
                       cmd11.ExecuteNonQuery();
                       ClsConnection.Conn.Close();

                   }

can any1 help plzzzzz