Count the Rows of a Filtered Tablix

Been having some major ball aches with SSRS (SQL Server Reporting Services) recently -specifically around trying to hide elements and filter data.

In this instance, I needed to hide a row in a group if there were no rows in the filtered tablix. This is the process I followed:

1. Added a column to the tablix and set the column visibility to hidden

2. Added a text box to the header row and set the expression for it to: =CountRows()

3. Set the row visibility expression to this:

=(Int32.Parse(ReportItems!txtUsageDataRowCount.Value) <= 0)

An extra to note here is the use of ReportItems. It's a neat way of referring to a value in a text box. It does only work for text boxes