cell formatting not applied after formula - apache-poi

Question

I'm using NPOI.
I read in an Excel workbook with two sheets that acts as a "template" for the result workbook I'll be generating. Sheet 0 is empty aside from some header rows and sheet 1 has a number of rows of formulas. The formulas generally refer to the sheet 0 and pull data from it.
I can't write directly into the template workbook because I'd be having to move rows out of the way and it would get ugly fast, so in code I create a new result workbook with two sheets. Based on a preset configuration file, I populate the sheet 0 of this result workbook with data, row by row, cloning the style and formulas of certain rows from the template workbook. Sheet 0 ends up filled with data, and sheet 1 is basically a row of formulas copied and adjusted relatively, typically pulling data from sheet 0 with a small calculation here or there.
All of my data in sheet 0 is text and cannot be interpreted as numeric, dates, etc. So I set my data cell types as String.
In code I then loop through all cells in sheet 1 and EvaluateInCell.
I do this to obviously evaluate the formulas, but also to remove the formulas and leave the copied/calculated results. This is just a requirement of the work I'm doing. We deliver the end results and no formulas.
I save the resulting workbook.
In general things look good, except where I have cell formatting, the formatting seems to not be applied.
The formatting IS there when I get the cell formatting properties in Excel.
For example I might have text data that is a date-time in my data that shows up as:
7/7/2016 9:54:55 AM
this IS what the original data text is, but on my formula sheet I have a custom cell format yyyymmdd.
And yet, the cell still shows: 7/7/2016 9:54:55 AM
In Excel I then do something like manually edit the value, for example delete the last 'M' and retype 'M' and hit enter, that cell changes to the desired format and shows:
20160707
So again, the formatting IS there, it's just not applied.
I don't want to have to manually edit cells, or do anything once the workbook is opened in Excel by my customers. I want the resulting workbook to open up with the values formatted.
I've tried a few things that seemed like a shot in the dark, like:
this.ResultWorkbook.GetCreationHelper().CreateFormulaEvaluator().EvaluateAll();
((XSSFWorkbook)this.ResultWorkbook).SetForceFormulaRecalculation(true);
But this didn't help.
Any thoughts?

Answer 1

can you try either of this apprioach while setting the formula for cell
Approach 1
ICellStyle dateCellStyle = workbook.CreateCellStyle();
dateCellStyle.DataFormat = workbook.CreateDataFormat().GetFormat("yyyymmdd"); // Or prefix single quote for data when writing it to excel file like 'yyymmdd ex: '20160707
Approach 2
XSSFCellStyle dateCellStyle = (XSSFCellStyle)workbook.CreateCellStyle();
XSSFDataFormat dateDataFormat = (XSSFDataFormat)workbook.CreateDataFormat();
dateCellStyle.SetDataFormat(dateDataFormat.GetFormat("yyyymmdd"));

Answer 2

I ended up looking at the template Excel file's cell I'm writing into. It looks like if it's not DateUtil.IsCellDateFormatted and the cellStyle.DataFormat is not 0x31 (text based on BuiltInFormats), then it must be numeric.
Based on that I try to convert my text to DateTime or double as applicable, and call SetCellValue with those converted variables. Otherwise I write the text.
This seems to be working for cases I've encountered.