private static string GetFileEncryptionError(string inputFilePath) { if (Directory.Exists(inputFilePath)) { return(null); } if (!File.Exists(inputFilePath)) { return(_fileDoesNotExist); } bool?validMagicBytes = FileHandling.IsKryptorFile(inputFilePath); if (validMagicBytes == null) { return(_fileInaccessible); } if (FileHandling.HasKryptorExtension(inputFilePath) || validMagicBytes == true) { return("This file is already encrypted."); } return(null); }