Crown Prince Frederik wasn't the only one with double the dates for the concert event; Crown Princess Victoria arrived with both her brother, Prince Carl Philip, and her then-fiancé Daniel Westling in tow.
Victoria's dress, from Pär Engsheden, is made from layers of ruffly stripes in the palest of pastels and grays, exploding into a tail feather train just waiting for a shake. It was a repeat, also worn for the King's Dinner during the Nobel festivities in 2008:
So apparently, this dress was assigned light blue sash with pearls and diamonds duty. That's the Danish Order of the Elephant in the 2010 photos and the Swedish Order of the Seraphim above, nearly identical except for which shoulder they are worn over; Prince Carl Philip is wearing the Seraphim sash, if you were wondering why his and Victoria's are going in opposite directions. And for tiaras, we have the Diamond Bandeau in 2008 and the Four Button Tiara in 2010.
I think it works pretty well in that capacity, but the train does give me pause. The pale color scheme gives it less of a showgirl flair than, say, Princess Marie's similar train in hot pink, but it's still a downright hazardous design. And I mean that literally, as you can see at about the 3:27 mark in the video below, when it appears Carl Philip steps on her tail on the way up the steps and nearly brings the house down. Brothers, you just can't teach them anything.
She recovers with a laugh, but maybe the dress didn't. I don't think we've seen it since.