Can I use this expression in the sense of 'sorted in ascending order'? The context is programming: sorting a data-structure or results of a query.
It may technically be an acceptable adverb formation, but it is terribly uncomfortable. I would stick with "sorted in ascending order", as it would be readily understood by a larger audience than "ascendingly". Use of "ascendingly" would likely cause unnecessary confusion in your target audience: i.e. "What did they just say?". This would distract from your message.