Including blank cells in worksheet

ExcelEngine excelEngine = new ExcelEngine();

IApplication application = excelEngine.Excel;

application.DefaultVersion = ExcelVersion.Excel2013;

IWorkbook workbook = application.Workbooks.Create(1);

IWorksheet worksheet = workbook.Worksheets[0];

worksheet[1, 1].Text = "";

worksheet[1, 2].Text = "";

using (FileStream fileStream = new FileStream(filePath, FileMode.CreateNew))

{           

    worksheet.SaveAs(fileStream, ";", Encoding.Default);                                                               

}

workbook.Close();

excelEngine.Dispose();           

Output expected: ;;

How can I fix?