ReactiveUI - The type 'IScheduler' is defined in an assembly that is not referenced - reactiveui

Question

I'm trying to subclass ReactiveList so it responds to changes in a ReactiveDictionary I have written, rather than a parent List.
This is the class and constructor signature for the ReactiveList subclass.
public class ReactiveDictionaryDerivedList<TKey, TValue, TDerived> : ReactiveList<TDerived>, IReactiveDerivedList<TDerived>
{
public ReactiveDictionaryDerivedList(
IReadOnlyReactiveDictionary<TKey, TValue> dict,
Func<TValue, TDerived> selector,
Func<TValue, TDerived, bool> derivedValueFinder,
IScheduler scheduler)
{
}
Here are the dependencies I have in the project. Notice that I'm using the 4.0.0 preview release of System.Reactive, since this is installed by the ReactiveUI 8.0.0 alpha. (I'm using the ReactiveUI alpha as this seems to be what is recommended these days)
<packages>
<package id="ReactiveUI" version="8.0.0-alpha0113" targetFramework="net452" />
<package id="ReactiveUI.WPF" version="8.0.0-alpha0113" targetFramework="net452" />
<package id="Splat" version="2.0.0" targetFramework="net452" />
<package id="System.Reactive" version="4.0.0-preview00001" targetFramework="net452" />
</packages>
The problem is that the class doesn't compile because of the error:
error CS0012: The type 'IScheduler' is defined in an assembly that is not referenced.
You must add a reference to assembly 'System.Reactive.Interfaces, Version=3.0.1000.0,
Culture=neutral, PublicKeyToken=94bc3704cddfc263'.
Any ideas how to resolve would be appreciated. Advice on the recommended versions for ReactiveUI and System.Reactive would also be nice.

Answer 1

In my WPF app I had to install the System.Reactive.XXXXX packages with version 4.0.0-preview00001 (Core, Interfaces, Linq, PlatformServices, Windows.Threading, Windows.Forms).
All these packages come with the System.Reactive.Compatibility package (nuget link):
Reactive Extensions (Rx) Compatibility Library for enabling v3 apps to
work with v4
You should try using it in your project.

Answer 2

Unfortunately something fishy is going on with dependencies at the moment. But for the current 8.0 version it's recommended to install System.Reactive 3.1. That's the only version 8.0 is tested against.
If you start using PackageReference for your projects, you won't need to define the System.Reactive dependency yourself, but it's picked up by the package manager. But that might not work (yet?) with WPF.
See: https://learn.microsoft.com/en-us/nuget/consume-packages/package-references-in-project-files