[BUG] When running NET6 WPF, it errors: Could not load type 'System.Reactive.Concurrency.DispatcherScheduler'

[drepamig]

--SEE SECOND COMMENT--

Describe the bug
I'm trying to test a project using the latest preview of NET6. When I launch my WPF project that uses RxUI, it crashes with the error:

System.TypeInitializationException: 'The type initializer for 'ReactiveUI.RxApp' threw an exception.'

TypeLoadException: Could not load type 'System.Reactive.Concurrency.DispatcherScheduler' from assembly 'ReactiveUI, Version=15.1.0.0, Culture=neutral, PublicKeyToken=null'.

I did some investigation and it appears as the HAS_WPF flag in ReactiveUI.csproj is limited to net5.0-windows:

  <PropertyGroup Condition=" $(TargetFramework.StartsWith('net46')) or $(TargetFramework) == 'net47' or $(TargetFramework) == 'net471' or $(TargetFramework) == 'net5.0-windows'">
    <DefineConstants>$(DefineConstants);HAS_WPF</DefineConstants>
  </PropertyGroup>

... and since HAS_WFP evaluates to false, it fails to create the dispatcher as expected.

I cloned the source and added net6.0-windows to the condition, built a test version, and it still failed. However, when I changed the <targetframework> in my csproj...

 from: `<TargetFramework>net6.0-windows</TargetFramework>`
 to: `<TargetFramework>net6.0-windows10.0.19041</TargetFramework>`

...everything works fine. I'm not sure why that is though. It was a shot in the dark based on some advice given on here to people during the migration from netcore 3.1 to NET5.0

Steps To Reproduce
Provide the steps to reproduce the behavior:

1. Create a NET6.0 WPF project with RxUI
2. Use something via RxApp (i.e. RxApp.SuppressViewCommandBindingMessage = true)
3. See error

Expected behavior
Run correctly on NET6 WPF instead of only NET6 MAUI (I think?).

Environment

• OS: Windows 10 Enterprise 20H2
• Version RxUI 15.1.1

[drepamig]

Well, reviewing my post, I realize I never tried just changing my csproj:

from: <TargetFramework>net6.0-windows</TargetFramework>
to: <TargetFramework>net6.0-windows10.0.19041</TargetFramework>

The special version that added the condition to HAS_WPF seems to un-needed. I just happened to try that first and never removed it before testing the other option. Sorry for the confusion.

[ChrisPulman]

We are working on getting .net 6 support for Winforms and WPF via #2887 this should be ready in the next couple of days.
Please see https://github.com/dotnet/designs/blob/main/accepted/2021/net6.0-tfms/net6.0-tfms.md for the valid list of Target Frameworks for .net 6.0

[glennawatson]

Yeah the 10.0.19041 is the version that code is included from Rx.net. I didn't want all the support calls about people forgetting to add that version so I added the Rx code into our repo for those doing -windows.

You can see #2887 I already handle this scenario

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