SSRS Expression to compare two values and get data from another dataset

Question

Hi,
I have a requirement where in i need to compare a value of a dataset (not the one which table is poiting to)
with the value of a text box, and return the count if it matches else 0, the expression is as below. Here 
industryName and recCount are from the dataset ds_MedimOrLowImpactEntities.  whats wrong in this expression
=Sum(IIF(Fields!industryName.Value = reportItems!hpapra_name.Value, Fields!RecCount.Value, 0), "ds_MediumOrLowImpactEntities")
This is the error that i am getting:
Any help on this is appreciated
Kruthi Hegde

Answer 1

Hi Kruthi,
After testing the issue in my local environment, I can reproduce it. Just the error message said, “Aggregate function can be used only on report items contained in page headers and footers”. So the sum function that contains report items should be stayed
at page headers or footers. Besides, you said the hpapra_name textbox contain a field from another dataset, not the ds_MedimOrLowImpactEntities dataset. While in Reporting Services, Report item expressions can only refer to other report items within the same
grouping scope or a containing grouping scope. So consider the two issues, we should use some other expression to instead the “reportItems!hpapra_name.Value” expression.
Take a look at the "Looking up values from another dataset" topic here:
http://msdn.microsoft.com/en-us/library/ms159673.aspx#LookupFunctions
Hope this helps.
Thanks,
Katherine Xiong
Katherine Xiong
TechNet Community Support