How to export datatable data to existing excel sheet file

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C#

MS-Excel

OpenXML

read/write

I have wondering for a way to export and append data-table to existing excel file using C# and OpenXml. I am generating product report sheets and getting problem in Saving that new data. After append a new row successfully, when I read Excel again or Open that particular Excel file I cannot find newly inserted row in file. (means data is not properly written).

If you can provide sample code for this,Its very useful for me.
Thanks In Advance.

What I have tried:

private static void AddRow(SpreadsheetDocument spreadSheetDoc, DataTable table)
        {
            workbookPart = spreadSheetDocument.WorkbookPart;
            IEnumerable<sheet> sheets = spreadSheetDocument.WorkbookPart.Workbook.GetFirstChild<sheets>().Elements<sheet>();
            
            string relationshipId = sheets.Where(s => s.Name == sheetName).SingleOrDefault<sheet>().Id.Value;

            worksheetPart = (WorksheetPart)spreadSheetDocument.WorkbookPart.GetPartById(relationshipId);
            workSheet = worksheetPart.Worksheet;
            sheetData = workSheet.GetFirstChild<sheetdata>();

            lastRow = sheetData.ChildElements.Count - 1;

            var sheet = workbookPart.Workbook.Descendants<sheet>().FirstOrDefault();

            if (sheet == null)
                throw new Exception("No sheed found in the template file. Please add the sheet");

            int rowIndex = lastRow + 1, colIndex = 0;

            List<string> columns = new List<string>();

            foreach (System.Data.DataColumn column in table.Columns)
            {
                columns.Add(column.ColumnName);
            }

            foreach (System.Data.DataRow dsrow in table.Rows)
            {
                Row row = new Row();
                foreach (String col in columns)
                {
                    DocumentFormat.OpenXml.Spreadsheet.Cell cell = new Cell();
                    cell.DataType = DocumentFormat.OpenXml.Spreadsheet.CellValues.String;
                    cell.CellValue = new DocumentFormat.OpenXml.Spreadsheet.CellValue(dsrow[col].ToString());
                    row.AppendChild<cell>(cell);
                }
                sheetData.InsertAt<row>(row, rowIndex);
            }
            workbookPart.Workbook.Save();
        }