System.NotSupportedException in System.Reactive.dll

Question

I'm new to Rx.Net and Dynamic Data and I'm currently facing a following problem by using these Reactive UI Extensions.

What I try to achieve:

1. Apply the Dynamic's Data Filter operation on TaskpoolScheduler (or in general filtering the incoming data asynchronously)
2. Adding data to SourceList from a background thread

However, when the SourceList is getting filled with the data from a different task I get the 'System.NotSupportedException' in System.Reactive.dll error. So I have to use the Dispatcher Thread.

How to fix this?

A minimal working example:

using DynamicData;
using ReactiveUI;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Reactive.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace ReactiveExtensionsTest
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        private readonly ReadOnlyObservableCollection<DataModel> _items;

        public ReadOnlyObservableCollection<DataModel> Items => _items;

        public MainWindow()
        {
            InitializeComponent();

            DataContext = this;

            var bgDataService = new BackroundDataService();
            bgDataService
                .Connect()
                .ObserveOn(RxApp.TaskpoolScheduler)
                .Filter(x => x.IntA % 2 == 0)
                .ObserveOn(RxApp.MainThreadScheduler)
                .Bind(out _items)
                .Subscribe();
        }


    }

    class BackroundDataService : IBackgroundDataService
    {
        private readonly SourceList<DataModel> _data = new SourceList<DataModel>();

        public IObservable<IChangeSet<DataModel>> Connect() => _data.Connect();

        public BackroundDataService()
        {
            Task.Factory.StartNew(async () =>
            {
                int length = 100_000;
                for (int i = 0; i < length; i++)
                {
                    _data.Add(new DataModel { IntA = i, StringB = "B {i}" });
                    await Task.Delay(200);
                }
            });
        }

    }

    internal interface IBackgroundDataService
    {
        IObservable<IChangeSet<DataModel>> Connect();
    }

    public class DataModel
    {
        public int IntA { get; set; }

        public string StringB { get; set; }
    }
}

The Items property is bound to a ListBox as following <ListBox ItemsSource="{Binding Items}"/>

Answer 1

Have you tried

    var bgDataService = new BackroundDataService();
            bgDataService
                .Connect()
                .ObserveOn(RxApp.TaskpoolScheduler)
                .Filter(x => x.IntA % 2 == 0)
                .Bind(out _items)
                .SubscribeOn(RxApp.MainThreadScheduler);

Might be worth a try.