When 1 file is downloaded so it cannot be downloaded by others or other system(it should get locked)

Jul 13 2011 7:28 AM

I am download file from FTp by File watcher .when 1 file is downloading so others can not download that file

How can i do this i have no idea one of my friend telling use locking mechanism

will it help me or something else should be used

I am working with C# (windows application)

Thanks