Write to an existing excel file, while retaining it's formatting about npoi

[baiyunchen]

@CharlesOkwuagwu
On new XSSFWorkbook(stream),NOPI.Core will close the stream(NPOI has the same problem) ,so when writing,the file stream will not be modified,this should be a bug, but I do not currently know how to fix it.

But for your current logic,you can rewrite the flowing code,I simply tested,it can run perfectly.

public void WriteExcel()
{
    string outputFileName = $@"xxx\template-{DateTime.Now.Ticks.ToString()}.xlsx";
    using (var templateStream =new FileStream(@"xxx\template.xlsx", FileMode.Open, FileAccess.Read))
    {
        var excel = new XSSFWorkbook(templateStream);
        var cell = excel.GetSheetAt(0).GetRow(2).GetCell(2);
        cell.SetCellValue("Issue 33");

        using (var outputStream = new FileStream(outputFileName, FileMode.Create, FileAccess.Write))
        {
            excel.Write(outputStream);
        }
    }
    using (var outputStream = File.OpenRead(outputFileName))
    {
        var excel = new XSSFWorkbook(outputStream);
        var cell = excel.GetSheetAt(0).GetRow(2).GetCell(2);
        Console.WriteLine(cell.ToString()); //here can console Issue 33
    }
}

Hope can help you !

[yang-xiaodong]

@baiyunchen
Hi, yunchen
I'm on a business trip recently. Can you see what the problem is?

[CharlesOkwuagwu]

thanks.