NPOI Summary Information

npoisi.cs

/// See https://stackoverflow.com/questions/11143303/how-to-set-author-name-to-excel-file-using-poi
public static void SetAuthor(this IWorkbook workbook, string author)
{
    if (workbook is NPOI.XSSF.UserModel.XSSFWorkbook)
    {
        var xssfWorkbook = workbook as NPOI.XSSF.UserModel.XSSFWorkbook;
        var xmlProps = xssfWorkbook.GetProperties();
        var coreProps = xmlProps.CoreProperties;
        coreProps.Creator = author;
        return;
    }

    if (workbook is NPOI.HSSF.UserModel.HSSFWorkbook)
    {
        var hssfWorkbook = workbook as NPOI.HSSF.UserModel.HSSFWorkbook;
        var summaryInfo = hssfWorkbook.SummaryInformation;

        if (summaryInfo != null)
        {
            summaryInfo.Author = author;
            return;
        }

        var newDocInfo = NPOI.HPSF.PropertySetFactory.CreateDocumentSummaryInformation();

        var newInfo = NPOI.HPSF.PropertySetFactory.CreateSummaryInformation();
        newInfo.Author = author;

        hssfWorkbook.DocumentSummaryInformation = newDocInfo;
        hssfWorkbook.SummaryInformation = newInfo;

        return;
    }
}