Let me start by excusing myself for an absence of posting lately. It has been very busy recently in my private life. Becoming a father certainly makes you more prone to setting priorities 
Lately I have been making several NAV2013 reports, so maybe it is time to make another post with issues you might run into, or in general even certain methods which could be convenient for you to know about.
1. Building the dataset
When creating a document layout, I was using an Integer DataItem below my lines to show some more information (in case it was needed). Using PRS, I had a function in a CodeUnit which would build my temporary record used for the DataItem, and loop it accordingly with the code below
--- Integer - OnPreDataItem --- SETRANGE(Number,1,TempRecord.COUNT); --- Integer - OnAfterGetRecord --- IF Number = 1 THEN TempRecord.FINDSET ELSE TempRecord.NEXT;
The call to fill my TempRecord was also returning a Boolean, to add to my dataset and make the table visible altogether or not (otherwise my headers would be printed).
So I added the single line call to the columns filling the TempRecord and the Dataset with my Boolean…
When running my report, I was nicely presented with 2 records of my Integer DataItem, however both times containing the last record instead of 2 different records.
Debugging showed actually looping through the TempRecord nicely, until I noticed that everytime a row for the dataset needed to be created, NAV loops through all your columns and runs the business logic if it points to a function instead of a field. Meaning that for each time, it clears my TempRecord and fills it again, positioning it at the last inserted record at the same time…
This sort of made sense of course (well, I hoped it would have cached the data of the other DataItems…), but has the logical result that I could not make the single line call in my dataset, but in code, preserving the result of the function in a Report variable and add that one to my dataset…
So remember, try to buffer everything possible in your dataset, a lot of unnecessary code could be run otherwise for each record in your dataset, instead of just the times necessary.
2. Copying Tablixes
The TempRecord above also needed to be in a table, which almost looked like the table used for my document lines, so logically I copied that one. The source table however had a lot of logic about visibility in it, which gets copied nicely. I started changing sorting, filters, rows, … from my new table until I had what I wanted and started to test again, just to notice that no data whatsoever was printed…
This took some time to figure out as well, but running through the XML of my RDLC revealed that some hidden properties of deleted rows were actually not deleted in the XML and no longer accessible from the design view.
Again, another bullet point to our reminder list: Try not to copy Tablixes , since they might get corrupted. The only way to be sure your table is created the way you want it, is to start from a blank one, which is a bit more work. But let’s be honest… it’s still pretty much manageable and not that much more work (or even less work in the end/long run)