I am trying to use Open XML to create a file but when trying to add just the first row of headers the file is being corrupted and I am unable to open, can anyone tell me what I am doing wrong here?
using (SpreadsheetDocument spreadsheetDocument = SpreadsheetDocument.Create("C:\\testpdfs\\mytest.xlsx", 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>();
    worksheetPart.Worksheet = new Worksheet(new 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 = ViewBag.Title
    };
    Row row = new Row() { RowIndex = 1 };
    Cell header1 = new Cell() { CellReference = "A1", CellValue = new CellValue("Interval Period Timestamp") };
    row.Append(header1);
    Cell header2 = new Cell() { CellReference = "A2", CellValue = new CellValue("Settlement Interval") };
    row.Append(header2);
    Cell header3 = new Cell() { CellReference = "A3", CellValue = new CellValue("Aggregated Consumption Factor") };
    row.Append(header3);
    Cell header4 = new Cell() { CellReference = "A4", CellValue = new CellValue("Loss Adjusted Aggregated Consumption") };
    row.Append(header4);
    sheet.Append(row);
    sheets.Append(sheet);
    //sheet.Append(row);
    workbookpart.Workbook.Save();
    // Close the document.
    spreadsheetDocument.Close();
    return View();
}