Hi Guys,

I found something interesting for the situation on Micrososft.com

https://docs.microsoft.com/en-us/sql/reporting-services/custom-assemblies/initializing-custom-assembly-objects?view=sql-server-ver15

It says "[...]  The Parameters, Fields and ReportItems collections are not available to you at the point in the...

Hi Brian,

that whas it!

Adding any Field-Result solved the issue, now my function is running as expected!

Best wishes, Mirko