/// <summary> /// Check if the user has already logged in /// </summary> /// <returns>username string if success, otherwise null</returns> private static string GetLoggedInUsername() { // first check if 'username' variable is in session if (HttpContext.Current.Session[UsernameAccessString] != null) { string username = (string)HttpContext.Current.Session[UsernameAccessString]; // now check for the 'username' in the database for additional check DataTable loginUserTable = DataAccessLayer.SelectCommand(DataAccessLayer.SelectCommandString( "Username", LoginTable, "Username = :username"), new CommandParameter(":username", username)); if (1 == loginUserTable.Rows.Count) { return(username); } // clear session state because it is not available in the database HttpContext.Current.Session.Clear(); CurrentInstance.Reset(); } return(null); }