private void initialflightlist()
        {
           items = new ObservableCollection<item>();

            var bk = new BackgroundWorker();
            bk.DoWork += async (s, e) =>
            {
                string connectionString = "##";
                using (OracleConnection connection = new OracleConnection())
                {
                    try
                    {
                        connection.ConnectionString = connectionString;
                        using (OracleCommand command = connection.CreateCommand())
                        {
                            string sql = $"sql";

                            command.CommandText = sql;

                            if (connection.State != ConnectionState.Open)
                                await connection.OpenAsync().ConfigureAwait(false);

                            DbDataReader reader = await command.ExecuteReaderAsync().ConfigureAwait(false);
                            if (reader.HasRows)
                            {
                                while (await reader.ReadAsync().ConfigureAwait(false))
                                {
                                    Application.Current.Dispatcher.Invoke(DispatcherPriority.Render, (Action)(() =>
                                     {
                                         items.Add(new item
                                         {
                                             item1 = Convert.ToString(reader["fld1"]),
                                             item2 = Convert.ToDateTime(reader["fld2"])
                                         });
                                     }));
                                }
                            }
                        }
                    }
                    catch (Exception ex)
                    {
                        //MessageBox.Show(ex.Message);
                    }
                    finally
                    {
                        if (connection.State == ConnectionState.Open)
                            connection.Close();
                    }
                }
            };
            bk.RunWorkerAsync();
            OnPropertyChanged("items");
			}

items=tempitems;