preprocessor directives giving either error or warning

I've never really had a cause to use these before, so I may be missing something really simple. Hopefully I won't be too embarrassed!

 // This will not compile because FileLocation is already defined.
 #if UNITY_EDITOR
 private static string FileLocation { get { return Application.dataPath; } }
 #endif
             
 #if UNITY_STANDALONE    
 private static string FileLocation { get { return Application.persistentDataPath; } }
 #endif

 
 // meanwhile, this gives an unreachable code warning on the latter return(s)
 private static string FileLocation {    
     get {
         #if UNITY_EDITOR
             return Application.dataPath;
         #endif
         
         #if UNITY_STANDALONE
             return Application.persistentDataPath;
         #endif
         
         return Application.persistentDataPath;
     }
 }

Can someone who knows what they're doing tell suggest a warning-free approach to getting this behavior? And, since this is new territory for me, double-check my assumption that this is a cross-platform ironclad way to grab my game's safe "save" directory?

As a bonus, how about the code below for cross-platform path composition? This okay too?

 public static char DSep { get { return  System.IO.Path.DirectorySeparatorChar; } }

Big thanks for any assistance,