Display records from Table B if and only if a single row of Table A is selected

[wcarter]

I have two tables, one is a summary of values and the other is detailed values by date and sub-category. They are connected by an id-date key column. When I have a single table and want to display it at two different detail levels I can use a measure that returns true if a single value is selected or false if no single value is selected and use that as a filter on the detailed view so that it doesn't show anything unless a single record is selected in the summary view. When I try this same technique for my current scenario, where I have two separate tables, Table B always displays records regardless of if a single value in Table A is selected or not.

See here, no row is selected in Table A on the left, so no records should display on the right, this screenshot is the bad behavior:

Desired behavior here where when no row is selected in Table A, nothing from Table B is displayed:

But when a record in Table A *is* selected, data from Table B is then displayed:

I've spent a whole mess of time on this and no combination of managing/removing filters or changing relationships used in my DAX query seems to work. I feel like I'm missing something obvious as to why this isn't working for me.

[lbendlin]

 Create a measure around HASONEVALUE or COUNTROWS for table A and then apply that measure as a visual filter to the table visual that shows columns from B.  In your data model Table A should not control table B.