I'm trying to add Allow Multi Values option to existing working report and getting this error Multiple selection not valid ..Because it's not supported by the data extension.
- Data source = Microsoft SharePoint List
I first time work with the report where Dataset is actual XML schema, so I see that this parameter set in Filter option. I pasted all info in below, not sure if this will work. I'm on SSRS 2014 with most recent updates. not sure if expression will help.




