There is a huge caveat to any discussion about the Canadiens trading David Desharnais, and that is of course that he is hurt right now. That being said, according to Louis Jean, Marc Bergevin and company are entertaining the idea of dealing him.
Selon sources, David Desharnais serait sur le marché. En dépit de sa blessure au pied, le #Canadien tenterait de l'échanger. @TVASports— Louis Jean (@LouisJean_TVA) February 29, 2016
I'm not sure what you could get for Desharnais, particularly thanks to the fact that he's hurt right now, but one thing you'd likely get is cap space. Even if it were a player for player trade, I'm sure that the player coming back would be on an expiring contract, so it would be about flexibility in the offseason.
Once more, that injury is a huge caveat, but we can't ignore that he is on the block. For sure, this will be something to follow in the coming hours, and Desharnais may be heading somewhere else before the deadline at 3PM Eastern time.