static void Main(string[] args)        {            //Create 一个Excel对象            HSSFWorkbook hssfWorkbook = new HSSFWorkbook();            //Create Excel的属性中的来源以及说明等            DocumentSummaryInformation dsi = PropertySetFactory.CreateDocumentSummaryInformation();            dsi.Company = "NPOI-1";            dsi.Category = "NPOI-2";            dsi.Manager = "NPOI-3";            //创建好的对象赋给hssfWorkbook,这样才能保证这些信息被写入文件            hssfWorkbook.DocumentSummaryInformation = dsi;            SummaryInformation si = PropertySetFactory.CreateSummaryInformation();            si.Subject = "NPOI SDK Example 1";            si.Title = "NPOI SDK Example 2";            si.ApplicationName = "NPOI SDK Example 3";            si.Author = "NPOI SDK Example 4";            si.LastAuthor = "NPOI SDK Example 5";            si.Comments = "NPOI SDK Example 6";            si.CreateDateTime = DateTime.Now.AddMonths(-2);            //创建好的对象赋给hssfWorkbook,这样才能保证这些信息被写入文件            hssfWorkbook.SummaryInformation = si;            //创建文件并写入            FileStream file = new FileStream(@"demo.xls", FileMode.Create);            hssfWorkbook.Write(file);            file.Close();        }