Christmas party dress

I'm helping our social committee with the Christmas party which is on the 3rd (a little too early for my taste). The theme: black and white ball. I need a little black dress for the event, one that is not too dressy nor too cold. I found the following two dresses, the first from Urban Outfitters and the other from Asos (my favourite online shop),there are dresses a plenty there. I'm off to search some more!