Dispatcher is null in WinUI Desktop in WinUI 3 Preview 4

[Berkunath]

Dispatcher of Page and other UI elements are return null in WinUI Desktop after upgrade of WinUI 3 Preview 4. We have to run async using Dispatcher. But Dispatcher returns null in WinUI Desktop but WinUI UWP returns proper value for Dispatcher. It works fine in WinUI 3 Preview3

await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, () => { // My Action here });

Expected behavior
Dispatcher should not be null or sugestion to Runasync

NuGet package version:

[Microsoft.WinUI 3.0.0-preview4.210210.4]

[marb2000]

@Berkunath Dispatcher and CoreDisptacher are null in the Preview 4. You should use DispatcherQueue instead.
Here you can find a demo that uses it.

[nickrandolph]

@marb2000 is there a reason why Dispatcher and CoreDispatcher are null? This seems to be an unnecessary breaking change for existing UWP style code?

[StephenLPeters]

Winui3 doesn't have a core window and Dispatcher and CoreDispather both relied on CoreWindow. Thus these APIs are no longer sufficient for the winui3 app model, DispatcherQueue is their replacement.

[fiftin]

Why Dispatcher was not marked as Deprecated?

I spent a lot of time until find this issue

[Slion]

Here is what it looks like now:

_ = DispatcherQueue.TryEnqueue(() => DoYourThing());

[LokiMidgard]

It could at least be mentioned in the Documentation.

[krschau]

This, and other similar APIs, are outlined here: Windows Runtime APIs not supported in desktop apps

[DRAirey1]

@Berkunath Dispatcher and CoreDisptacher are null in the Preview 4. You should use DispatcherQueue instead. Here you can find a demo that uses it.

#1 That link is broken
#2 The DispatcherQueue is null in my app.

[hdkesting]

After an attempt to upgrade a 4.8 UWP app to NET9 I got comments in the code:

// TODO Windows.UI.Core.CoreDispatcher is not longer supported. For more details see https://docs.microsoft.com/en-us/windows/apps/windows-app-sdk/migrate-to-windows-app-sdk/guides/threading

That link at least shows some details (still working on it...)

But an "obsolete" warning would have been more helpful.