public MainWindow() { InitializeComponent(); tableDatas = new List <string>(); tableDatas.Add("form"); tableDatas.Add("question"); tableDatas.Add("question_option"); UpdateTableData.ItemsSource = tableDatas; DeleteTableData.ItemsSource = tableDatas; formdata = new FormDAO(); questiondata = new QuestionDAO(); questionOptiondata = new QuestionOptionDAO(); resultdata = new ResultDAO(); usersdata = new UsersDAO(); MySqlConnection connection = MyMySQLConnection.ConnectionSingleton(); connection.Open(); formColumnNames = formdata.FindColumnNamesOnlyString(connection); questionColumnNames = questiondata.FindColumnNamesOnlyString(connection); questionOptionColumnNames = questionOptiondata.FindColumnNamesOnlyString(connection); resultColumnNames = resultdata.FindColumnNamesOnlyString(connection); connection.Close(); }