How to make the text bold in excel using open XML C#

See more:

C#

OpenXML

Hi
I am creating an excel, where i want to make some text bold in one of the columns for which i tried with below code and its not working.

Can some one suggest me where am i doing wrong.

Regards
Sampath.

What I have tried:

SpreadsheetDocument spreadsheetDocument = SpreadsheetDocument.Create(m_SchemaFileName, SpreadsheetDocumentType.Workbook);
                // Add a WorkbookPart to the document.
                WorkbookPart workbookpart = spreadsheetDocument.AddWorkbookPart();
                workbookpart.Workbook = new Workbook();

                // Add a WorksheetPart to the WorkbookPart.
                WorksheetPart worksheetPart = workbookpart.AddNewPart<WorksheetPart>();
                SheetData sheetData = new SheetData();
                worksheetPart.Worksheet = new Worksheet(sheetData);

                
                // Add Sheets to the Workbook.
                Sheets sheets = spreadsheetDocument.WorkbookPart.Workbook.
                    AppendChild<Sheets>(new Sheets());

                // Append a new worksheet and associate it with the workbook.
                Sheet sheet = new Sheet()
                {
                    Id = spreadsheetDocument.WorkbookPart.
                    GetIdOfPart(worksheetPart),
                    SheetId = 1,
                    Name = "ClassMap"
                };
                 Row row4 = new Row() { RowIndex = 4 };
                Cell header4 = new Cell() { CellReference = "B4", CellValue = new CellValue("ClassIdentifyingLabel"), DataType = CellValues.String };
                AddBold(spreadsheetDocument, header4);
                row4.Append(header4);            

public CellFormats AddCellFormat(CellFormats cf, Fonts fs)
        {
            cf = new CellFormats();
            CellFormat cellFormat2 = new CellFormat() { NumberFormatId = 1, FontId = (UInt32)(fs.Elements<Font>().Count() - 1), FillId = 0, BorderId = 0, FormatId = 0, ApplyFill = true };
            cf.Append(cellFormat2);
            return cf;
        }
        public  void AddBold(SpreadsheetDocument document, Cell c)
        {
            Fonts fs = AddFont(document.WorkbookPart.WorkbookStylesPart.Stylesheet.Fonts);
            CellFormats cf =  AddCellFormat(document.WorkbookPart.WorkbookStylesPart.Stylesheet.CellFormats,fs);
            c.StyleIndex = (UInt32)(cf.Elements<CellFormat>().Count() - 1);
        }