private static SpreadsheetDocument CreateWorkbook(Stream stream)
    {
        // Create the Excel workbook
        var spreadSheet = SpreadsheetDocument.Create(stream, SpreadsheetDocumentType.Workbook, false);

        // Create the parts and the corresponding objects
        // Workbook
        spreadSheet.AddWorkbookPart();
        spreadSheet.WorkbookPart.Workbook = new Workbook();
        spreadSheet.WorkbookPart.Workbook.Save();

        // Shared string table
        var sharedStringTablePart = spreadSheet.WorkbookPart.AddNewPart<SharedStringTablePart>();
        sharedStringTablePart.SharedStringTable = new SharedStringTable();
        sharedStringTablePart.SharedStringTable.Save();

        // Sheets collection
        spreadSheet.WorkbookPart.Workbook.Sheets = new Sheets();
        spreadSheet.WorkbookPart.Workbook.Save();

        // Stylesheet
        var workbookStylesPart = spreadSheet.WorkbookPart.AddNewPart<WorkbookStylesPart>();
        workbookStylesPart.Stylesheet = new Stylesheet();
        workbookStylesPart.Stylesheet.Save();


        return spreadSheet;
    }

    private static WorksheetPart AddWorksheet(SpreadsheetDocument spreadsheet, string name)
    {
        // Add the worksheetpart
        var worksheetPart = spreadsheet.WorkbookPart.AddNewPart<WorksheetPart>();
        worksheetPart.Worksheet = new Worksheet(new SheetData());


        uint sheetId = 1;
        var sheets = spreadsheet.WorkbookPart.Workbook.GetFirstChild<Sheets>();
        if (sheets.Elements<Sheet>().Any())
        {
            sheetId = sheets.Elements<Sheet>().Select(s => s.SheetId.Value).Max() + 1;
        }

        // Add the sheet and make relation to workbook
        var sheet = new Sheet
        {
            Id = spreadsheet.WorkbookPart.GetIdOfPart(worksheetPart),
            SheetId = sheetId,
            Name = name
        };

        sheets.Append(sheet);

        worksheetPart.Worksheet.Save();
        spreadsheet.WorkbookPart.Workbook.Save();

        return worksheetPart;
    }