How to know first and last record in a group for calculation purposes

rbuser

Hi,

I have a group band set up. Basically for each detailed record I am
creating a string (to be exported to a file). However, the first record of
the group nees to be prefixed with some control characters, and the last
record needs to be suffixed with some contril characters. What is the best
way to achieve this? I have tried a group count field to work out how many
records there are but it appears to increment itself as it goes through each
record (as opposed to showing the total number in the group - even using
lookahead).

Thanks

Alex

nicocizik

Hi Alex,

ReportBuilder does not have any built-in feature to pre-count the number of
records in a group. One option might be to create a two pass report and in
the first pass, keep track of what record each group breaks on. Perhaps
using the AfterGroupBreak event of the group or the
GroupFooterBand.BeforePrint event. Then you can use this information during
the second pass to determine the first and last record of a group.

--
Regards,

Nico Cizik
Digital Metaphors
http://www.digital-metaphors.com

rbuser

K will give that a go

Alex

rbuser

Hi,

Not sure how this would work. In the first pass are you saying keep an
array for each group break of what the recordcount was? If I had a thousand
group breaks thats a big array (especially to use with ReportBuilder where
calculations are slow). Or am i misinterpreting?

Just out of interest, how then would you handle the need t display
percentages, for example the percentage each group represents in percentage
terms out of the total. Is this not supported?

Regards

Alex

nicocizik

Hi Alex,


Yes this is what I was suggesting. As I mentioned before, ReportBuilder
wasn't designed to know how many records are in each group. It is easy to
alter the first record of a group using the AfterGroupBreak but the problem
lies with the last record of a group. All group events fire after this band
has been created.

As an alternative, you might try making changes to the components during the
first pass of the report using the group events (you will have to experiment
with different events to see if they fire at the proper time) so those
changes are reflected during the second pass.

I believe constructing a list of where each group will break is a more
elegant solution and will be easier to manage.

--
Regards,

Nico Cizik
Digital Metaphors
http://www.digital-metaphors.com

rbuser

Hi Nico,

Seems very limiting to not be able to calculate running percentages in a
report-writing tool, but lets work with that limitation. I need to know
then how do you create an array, I didnt think ReportBuilder supported array
type variable definitions.

Thanks

Alex

nicocizik

Hi Alex,

Keeping a running percentage of a group is very different from adding
control characters to the last detail of a group. . Perhaps I have
missunderstood what you were trying to accomplish from the beginning.

http://www.digital-metaphors.com/tips/percentage.zip


--
Regards,

Nico Cizik
Digital Metaphors
http://www.digital-metaphors.com

rbuser

Hi Nico,

I used the running percentage example as I envisaged that if you can do this
then you have a total count to also be able to identify the last record in a
group.

That percentage example, I tried it but it just kept calculating thousands
of pages. Is it for a particular RB version, we currently are requiring
this for V7? Also, is this an end-user report, can what you have done there
be achieved purely using the end-user capability?

Thanks

Alex

nicocizik

Alex,

Unfortunately we do not have an example that calculates percentage that
support RB 7. If you take a look at the code of the example you can see
that since the LookAhead property is set for the DBCalc components, these
values will be calculated during the first pass, and then can be used to
compare against the field value during the second pass. This bypasses the
need to know when the group starts or ends. In your case, needing to change
the value of certain components based on the total value, you could use the
same method however you still need to know where the last detail in the
group is going to be because you cannot change it once it has been
generated. This is why you will need to keep track of where these group
breaks are by either using the method I described before or perhaps manually
looking ahead in the data using the pipeline routines.

It is possible to create something similar to the total percentage example
completely in RAP if you would like to keep everything in an end-user app.

--
Regards,

Nico Cizik
Digital Metaphors
http://www.digital-metaphors.com