Đọc dữ liệu từ file Excel

// Chọn file Excel
     OpenFileDialog f = new OpenFileDialog();
     f.Filter = "Excel files (*.xlsx)|*.xlsx|All files (*.*)|*.*";
     f.FilterIndex = 1;
     f.RestoreDirectory = true;
     if (f.ShowDialog() == DialogResult.OK)
     {
          SplashScreenManager.ShowForm(typeof(frmLoading));
          FileInfo newFile = new FileInfo(f.FileName);
          Workbook workbook = new Workbook(f.FileName);
          Worksheet wordsheet = workbook.Worksheets[0];
          workbook.Worksheets.ActiveSheetIndex = 0;

          for (int i = 18; i <= wordsheet.Cells.Rows.Count; i++)
          {
                    
              if (wordsheet.Cells["B"i].Value.ToString().ToUpper() == "TỔNG CỘNG:")
              {
                   break;
              }
              string d = wordsheet.Cells["D"+i].Value.ToString();
                   
           }
     }