Require a Slicer for Data Output

[irnm8dn]

I have userd Power BI, with reasonable success, to create a directory for my organization.  As an example, a user selects a "Market", and below I have cards showing Address, Phone, Local Staff and Corporate Contacts.

I am trying to force a rule that the the slicer where a user selects a specific market must be selected to show data on the cards below.  Is there a DAX statement that I can use that require a user to select an option from the slicer, to "reveal" the supporting details.

Thanks in adavance!