CollectionView on WinUI platform

dg2k 1,381

I am converting a Xamarin app to .NET MAUI. CollectionView control is a major part of the design for displaying grouped items.

<CollectionView  
     Margin="6,6,6,48"  
     IsGrouped="True"  
     ItemsSource="{Binding Path=FolderCollection, Mode=OneWay}"  
     ItemsUpdatingScrollMode="KeepItemsInView"  
     SelectionMode="Multiple">  
  ...    
  
</CollectionView>

Everything works fine in Xamarin, both on latest releases of Android (SDK 31) and Windows UWP.
IDE is Visual Studio 2022 ver 17.3.0 Preview 2.

After carrying out all migrations for .NET MAUI, everything works as expected, except a toggling tap on CollectionView group item (so as to toggle items' visibility within a group) will crash the app on Windows with Unhandled Exception.

Exception: Microsoft.UI.Xaml.UnhandledException
Exception.ToString(): "Value does not fall within the expected range."
Exception.Message: "The parameter is incorrect."

The crash is traced to populating items list that is bound to CollectionView.ItemTemplate. XAML code for Xamarin and MAUI is identical.

On Android platform, on the other hand, everything works as expected, although Android has an unrelated issue which showed up with the latest MAUI 6.4.0 as reported here.

My question: is there a known issue with Microsoft.Maui.Controls.CollectionView on WinUI platform? If so, is there a workaround to this problem?

Leon Lu (Shanghai Wicresoft Co,.Ltd.) 67,781 Reputation points Microsoft Vendor

2022-06-21T09:23:33.06+00:00

To exclude the migration issue, you can create a blank Maui project, then achieve the same function. Is that work?

except a toggling tap on CollectionView group item (so as to toggle items' visibility within a group)

Can you share this part of code so that I can reproduce this issue? Do you use a Switch in GroupHeaderTemplate to control items’ IsVisible property?
I created a MAUI project, but it works without issues.
As noted in the Q&A FAQ: How to write a quality question.
dg2k 1,381 Reputation points

2022-06-21T09:29:24.027+00:00

Thank you @Leon Lu (Shanghai Wicresoft Co,.Ltd.) for the reply.
I shall create a demo project and share it with you. I may be a bit late due to work at hand at the moment. Will reply as soon as I can.
Leon Lu (Shanghai Wicresoft Co,.Ltd.) 67,781 Reputation points Microsoft Vendor

2022-06-22T08:43:22.33+00:00

OK, waiting for your mini demo. Here are known issues about CollectionView in windows platform. https://github.com/dotnet/maui/issues?q=is%3Aissue+ContentView+winui+is%3Aopen
dg2k 1,381 Reputation points

2022-06-24T18:35:09.917+00:00
Hello @Leon Lu (Shanghai Wicresoft Co,.Ltd.) ,

I managed to put together a .NET MAUI demo that shows CollectionView crash on Windows. A zipped project file is on my Public OneDrive storage folder which you can download at the following link:

https://1drv.ms/u/s!AlLAD5XYdzWn1sg0xED5V0L_Pn0VqQ?e=zgA2FS

Tapping on a CollectionView group will reveal the items in that group.
You can do that in succession for all groups.
You can also collapse the displayed items by tapping on the group again.

The crash problem arises on tapping to collapse followed by tapping to reveal.

The point at which it crashes is highlighted in the screenshot shown below. I have put that code in a separate file (MainPageViewModel.OnInfoFolderTapped.cs) under ViewModels folder.

Note:

This problem does not exist for Xamarin (I am migrating from Xamarin to .NET MAUI).

This problem does not exist for Android for .NET MAUI and this demo was not checked for Android as a non-issue.
Leon Lu (Shanghai Wicresoft Co,.Ltd.) 67,781 Reputation points Microsoft Vendor

2022-06-28T05:58:58.147+00:00

I run your demo and get the same issue. You can open an issue about this migrate issue in MAUI GitHub page: https://github.com/dotnet/maui/issues/new/choose