SelectionChangedCommandParameter is evaluated before SelectedItem updates in .NET 11

[SuthiYuvaraj]

Describe the bug

When using CommunityToolkit-generated commands with CollectionView, the SelectionChangedCommandParameter is evaluated before the SelectedItem binding is updated in .NET 11.
This behavior differs from .NET 10, where the bound SelectedItem was already updated when the command executed.
As a result, commands that rely on ViewModel properties (for example, SelectedItem) receive null or stale values.

• The command executes before the SelectedItem binding is updated.
• SelectionChangedCommandParameter is null or contains the previous value.
• This breaks scenarios that rely on ViewModel-bound properties inside the command.

Regression

8.0.3

Steps to reproduce

Run the attached sample.
Tap/select an item in the CollectionView.
Observe that SelectionChangedCommand is invoked.
Inspect the value of SelectionChangedCommandParameter.

Expected behavior

SelectionChangedCommandParameter should receive the updated selected item (or the updated ViewModel property) when the command executes.

Screenshots

No response

IDE and version

VS 2022

IDE version

No response

Nuget packages

• CommunityToolkit.Common
• CommunityToolkit.Diagnostics
• CommunityToolkit.HighPerformance
• CommunityToolkit.Mvvm (aka MVVM Toolkit)

Nuget package version(s)

8.0.4

Additional context

No response

Help us help you

Yes, I'd like to be assigned to work on this item

[Sergio0694]

Are you using MAUI by any chance? This feels like a bug there if so (you'll need to open an issue there and link this one).

[SuthiYuvaraj]

Yes, I am using .NET MAUI. However, the issue occurs only when using CommunityToolkit (RelayCommand). The CommandParameter is always null in this scenario. When using a plain INotifyPropertyChanged implementation, it works as expected. This also worked correctly in .NET 10 with CommunityToolkit 8.0.3, which suggests the issue is specific to the CommunityToolkit behavior rather than MAUI itself.

[Sergio0694]

Mh that's odd. I'm not sure how this can be related to a bug in the relay command per se (I suspect it might have to do more with the MAUI source generators perhaps). Could you try replacing the generated command with one you explicitly define? As in, literally just copy paste the generated command code and put it in your own viewmodel instead (and remove the attribute). Does that change the behavior at all? 🤔