How can I “specify a dataset aggregate” in this SSRS Expression?

Question

I need a row value in my SSRS report that is a calculated one based on a couple of fields that are already being used in the report. I want it to display in the textbox name

Answer 1

This is an interesting problem, because if you have ONLY 1 data set in your report, you don't need a table, you can directly reference a field that exists in that table.

However, if you have more than 1 data set then you must create a table, which may give you multiple rows. Then you might have to group by this one field, and hide the extra columns and rows. However, you CANNOT display this data in a TEXTBOX, you can however create a rectangle which can hold the table and another textbox. Or display the table directly.

Answer 2

It sounds like your Textbox has been added to an area of the report that isn't a "data region" (e.g. a table or list). A data region will have a reference to a particular report dataset as one of it's properties, so Reporting Services knows all field references inside that data region refer to that dataset. What this error is trying to say (in a rather verbose way) is:

• if you reference a field outside of a data region, that reference needs to be inside an aggregate expression such as Sum() - this is because the dataset may contain multiple rows for the field but outside of a data region a textbox can only display a single value.
• this aggregate expression must also include a reference to the report dataset that the field is coming from

So if field "WK1" was from dataset "MyDataset1", the expression to reference that field would look like:

=Sum(Fields!WK1, "MyDataset1")

See also: Using Dataset Fields Collection References in Expressions