Display date on card only when event is selected

[Anonymous]

I have a card on my dashboard that is meant to display the date of a selected event. The events are listed in a matrix along with other data. Currently the date on the card is making me select either the earliest or latest date. What I want is for the card to display the message "Select Event" when a specific event is not selected from the matrix. I've tried using slectedvalue, but I get an error message saying it will not work with variant type data. 

[Anonymous]

To clarify, I am looking for help writting the DAX code so that a card will only display a date when an event is clicked on in the matrix. When an event is not selected, I want the card to display the message "Select Event".

[Greg_Deckler · Accepted solution]

IF(HASONEVALUE(...),show event, "Select Event"

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