public string writePost(string forumName, string subForumName, int parentPostNo, string username, string title, string content) { List <string> input = new List <string>() { forumName, subForumName, username, title, content }; if (Constants.isValidInput(input) && Constants.isValidPost(title, content)) { lock (o) { User user = _um.getUserFromForum(forumName, username); if (user == null) { return("Wrong forum name or username."); } return(_fm.writePost(forumName, subForumName, parentPostNo, user, title, content)); } } return(Constants.INVALID_INPUT); }