If you use time machine - that would be the easiest way to get the file back (just go to the most recent back-up before you deleted the file).
If not, perhaps you could reinstall the file or X-code from your original system disks.
If you can't do either of these, then you are looking at data recovery software such as "data rescue 3". You might be able to use a demo, rather than pay, if you are just looking for one file.
P.S. The more you use your computer, the more likely it is to be overwritten and unretrievable.