I’ve never truly understood why we could explicitly commit a transaction, but we could only implicitly roll one back. There is a universe of difference between throwing an error (and ending the call stack), and rolling back (and continuing execution).
There was always a way to roll back and go on, sure. Wrap the entire thing in a if Codeunit.Run() block, throw an error as the last thing inside that codeunit, and there you go. Problem solved. Well, not quite.
In my two last posts, I laid out the technical design of the Preview Posting feature, and then showed how to simplify its design to get around the unwanted behavior of TryFunction.
One thing is obvious from these posts: Preview Posting wants to simulate posting of a document (or journal) to show what the results would be, but without leaving any actual trace in the database. In database lingo – we want the transaction to be rolled back.
Rolling back is no brainer. Simply throw an error, or do a silent abort, Except if there is COMMIT. In that case, no rolling back helps.
I have announced earlier that my today’s post will be about how to nest transactions in C/AL so that an inner COMMIT has no effect on the transaction as a whole, which can still be successfully rolled back.
That’s what this post is about.
In my yesterday’s article about the Preview Posting feature in Microsoft Dynamics NAV 2016 I said there are at least two ways to redesign it to avoid both the unnecessary complication and inherent dangers of the TryFunction feature behavior.
In my first post, I’ll show that it would have been perfectly possible to achieve exactly the same functionality without try functions. And it would take a total of one new line of code, one changed line of code, and six removed lines of code.
Let’s go and simplify it.
One of great new functional features of Microsoft Dynamics NAV 2016 is preview posting. It allows you to preview all the entries that would result from posting a document or a general journal.
Preview posting is not a simple thing. If it was, Microsoft would have delivered it years ago. There must be something in particular with NAV 2016 that powers preview posting, so I decided to investigate it and see exactly how it works.
I am not particularly happy with what I found out, but I have also learned some valuable lessons from it. In this post, I’ll share my findings.