my window file (dot w) was corrupted during saving because of Server error, the only file saved was the last successful compiled file (dot r) how can i recover my file....
This is a good reason to be backing up your source code. Go to backup in this situation.
Also if you are saving source code files to a folder with shadow copy running, you merely select a previous version.
You simply can't get a .w file back from .r.
Also if you are saving source code files to a folder with shadow copy running, you merely select a previous version.
You may also look for .ab files (the temp files that the AppBuilder created).
Or it may be time for a good SCM solution. (or at least a bad one).