Working with Office "open" XML - just how hard is it?

Question

I'm considering replacing a (very) large body of Office-automation code with something that works with the Office XML format directly. I'm just starting out, but already I'm worried that it's too big a task.

I'll be dealing with Word, Excel and PowerPoint. So far I've only looked at Word and Excel. It looks like Word documents should be reasonably easy to manipulate, but Excel workbooks look like a nightmare. For example...

In Word, it looks like you could delete a paragraph simply by deleting the corresponding "w:p" tag. However, the supplied code snippet for deleting a row in Excel takes about 150 lines of code(!).

The reason the Excel code is so big is that deleting a row means updating the row indexes of all the subsequent rows, fixing up the "shared strings" table, etc. According to a comment at the top, the code snippet is not even complete, in that it won't deal with a workbook that has tables in it (I can live with that).

What I'm not clear on is whether that's the only restriction that the sample code has. For example, would there also be a problem if the workbook contained a Pivot Table? Or a chart that references data from the same sheet? Or some named ranges? Wouldn't you also have to update the formulae for any cells (etc.) that referenced a row whose row index had changed?

[That's not to mention the "calc chain", which (thankfully) I think you can simply delete since it's only a chache that can be re-built.]

And that's my question, woolly though it is. Just how hard do you have to work do something as simple as deleting a row properly? Is it an insurmountable task?

Also, if there are other, similar issues either with Excel or with Word or PowerPoint, I'd love to hear about them now, before I waste too much time going down a blind alley. Thanks.

Wortham

Answer 1

Having worked with the Open XML SDK 2.0 for almost two years now I can say that doing seemingly trivial tasks can take many hours and sometimes days to figure out how to do it properly. For example, deleting an Excel row should be fairly straightforward and easy to do right? Nope because not only do you need code to delete your row, but then you have to update all the row indices, update any merged cell references, update hyperlink references, etc. Our internal delete method is close to 500 lines of code to just delete a row and I'm sure we don't have all the cases accounted for either.

The biggest complaint I have is the lack of documentation on how to do the most common tasks. The MSDN section on the Open XML SDK is very limited and whenever you need to do anything complicated you are really on your own. I've had to read the Open XML standard a lot to figure out what certain elements mean and how they should be implemented since I could find very little online.

The other challenging part is if you insert an element in a spot where it doesn't belong or put an invalid attribute on an element you will get a corrupt file when you try and open it. Most of the time you will not get any information on what caused the error and you will have to look at the Open XML standard spec to see what you did wrong.

If you need a fast turnaround time on converting that Office automation code into Open XML and what you are doing is not really basic, then I would say pass. If you have time and the patience to read up on the Word, Excel and PowerPoint XML structures and get familiar with how they relate then I say go for it. In my opinion it is really the only way to have very fine control over these office documents, but there will be a great learning curve when you start.

Oh and just for fun here is how much code is needed to add a comment to an Excel cell.

Hipolitohipp

Thanks. I did find some libraries for working with Excel, and for addressing some of the problems I mentioned in my question (and you repeated in your answer) - see my answer. – Wortham

Mr. @amurra, we're now in 2014, Open XML v2.5 (which is released at the end of 2012) is very promising as I read about it, my team lead is insisting to only use libraries which are maintained by Microsoft, what is you suggestion? – Bystander

I would quote from Microsoft website link, which is last updated on July 25, 2014: "The Open XML SDK 2.5 simplifies the task of manipulating Open XML packages and the underlying Open XML schema elements within a package. The Open XML SDK 2.5 encapsulates many common tasks that developers perform on Open XML packages, so that you can perform complex operations with just a few lines of code." – Bystander

I would agree with your team lead. Everything you need to do to manipulate an office document can be done with the open xml. The same cannot be said with a third party tool. If you run into a bug or issue you need to rely on a third party to fix it. MS is pretty good about fixing bugs on connect and you can have more faith that their libraries have been tested thoroughly. Also, if you switch the version in that link you posted to Office 2010 you will see the same description you quoted for v2.0. I don't think much changed in 2.5, but I'd trust MS libraries over third party libraries personally – Hipolitohipp

Why is Microsoft's OpenXML documentation still so terrible? Are they afraid if they made it easy to programmatically generate and modify .xlsx documents, people would create Excel clones with the help of the documentation, or what? – Lannielanning

Answer 2

Just for completeness, here are some libraries I found for working with Excel XML:

www.extremexml.com - a layer on top of the Open XML SDK classes; focusses on injecting data into an existing spreadsheet; handles many of the cross-reference problems I identified in my question. Open source but GPL2 not LGPL. Code looks nice, and documentation is excellent. Does not appear terribly active on codeplex though.

Closed XML - another layer on top of the Open XML SDK - again open source, but with a less restrictive license (MIT). Looks nice, and looks more "active" than the above.

SpreadsheetLight - from what I can tell, a closed-source library sitting atop the Open XML SDK classes. Targeted more at those looking to create a spreadsheet from scratch rather than making changes to existing spreadsheets.

Wortham

If you have performances troubles with Open XML based libraries, you may now consider EPPlus (LGPL) too. – Carnahan

Answer 3

Here is another third party library dedicated to working with OpenXML:

http://www.officewriter.com

In the example cited by amurra above of deleting Excel spreadsheet rows, this is a single method call with this tool. It updates formulas and all the other references for which it seems that 500 lines of code would be required for otherwise.

The OpenXML SDK itself is a great tool for very simple things, but you still have to concern yourself with a lot of the internals of the file format and packaging structure to get things really right.

Kyl

Answer 4

Here are some additional libraries that can manipulate with OOXML formats:
- GemBox.Spreadsheet (XLSX)
- GemBox.Document (DOCX)

Also GemBox published some articles that demonstrate how to manipulate with OOXML file format with pure .NET (without a use of any library), I think you'll find this interesting:

www.codeproject.com/Articles/15593/Read-and-write-Open-XML-files-MS-Office
(Introduction to SpreadsheetML format and an explanation on how we can read and write worksheet's cell content)

www.codeproject.com/Articles/649064/Show-Word-File-in-WPF
(Introduction to WordprocessingML format and demonstration on how we can read document's text)

Blandish

A link to a potential solution is always welcome, but please add context around the link so your fellow users will have some idea what it is and why it’s there. Always quote the most relevant part of an important link, in case the target site is unreachable or goes permanently offline. – Gneiss