From Excel to DataTable in C# with Open XML

I think this should do what you’re asking. The other function is there just to deal with if you have shared strings, which I assume you do in your column headers. Not sure this is perfect, but I hope it helps.

static void Main(string[] args)
{
    DataTable dt = new DataTable();

    using (SpreadsheetDocument spreadSheetDocument = SpreadsheetDocument.Open(@"..\..\example.xlsx", false))
    {

        WorkbookPart workbookPart = spreadSheetDocument.WorkbookPart;
        IEnumerable<Sheet> sheets = spreadSheetDocument.WorkbookPart.Workbook.GetFirstChild<Sheets>().Elements<Sheet>();
        string relationshipId = sheets.First().Id.Value;
        WorksheetPart worksheetPart = (WorksheetPart)spreadSheetDocument.WorkbookPart.GetPartById(relationshipId);
        Worksheet workSheet = worksheetPart.Worksheet;
        SheetData sheetData = workSheet.GetFirstChild<SheetData>();
        IEnumerable<Row> rows = sheetData.Descendants<Row>();

        foreach (Cell cell in rows.ElementAt(0))
        {
            dt.Columns.Add(GetCellValue(spreadSheetDocument, cell));
        }

        foreach (Row row in rows) //this will also include your header row...
        {
            DataRow tempRow = dt.NewRow();

            for (int i = 0; i < row.Descendants<Cell>().Count(); i++)
            {
                tempRow[i] = GetCellValue(spreadSheetDocument, row.Descendants<Cell>().ElementAt(i-1));
            }

            dt.Rows.Add(tempRow);
        }

    }
    dt.Rows.RemoveAt(0); //...so i'm taking it out here.

}


public static string GetCellValue(SpreadsheetDocument document, Cell cell)
{
    SharedStringTablePart stringTablePart = document.WorkbookPart.SharedStringTablePart;
    string value = cell.CellValue.InnerXml;

    if (cell.DataType != null && cell.DataType.Value == CellValues.SharedString)
    {
        return stringTablePart.SharedStringTable.ChildElements[Int32.Parse(value)].InnerText;
    }
    else
    {
        return value;
    }
}