public string logout(string userData, string filesData) { User user = JsonConvert.DeserializeObject <User>(userData); if (!theDal.isValid(user)) { return("User credentials are not valid."); } List <File> list = JsonConvert.DeserializeObject <List <File> >(filesData); foreach (var file in list) { if (theDal.contain(user, file)) { theDal.removeFile(file, user.name); } } theDal.logout(user); return("User logout."); }