XAMLC error in .NET 9 Preview 5 about maui HOT 12 CLOSED

All my custom ContentPage inherited XAML definitions are resulting in XAMLC errors.

When I surround the XAML with the ContentPage's Content node, it compiles. In that case, all my customization is not working.

Understand it's a Preview release but the basic scenario itself is failing. UT needs to be strengthened further.

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From what I can tell we're failing to compare type references because for some reason one of them is imported in the MPowerKit module:

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Something is odd here that it's showing DataTemplate for the baseClass coming from the MPowerKit.VirtualizeListView module. Looking at that assembly, I do not see any duplicated types, so what would be causing it to appear as though it's imported from that module?

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Verified this issue on VS Code 1.90.0 (9.0.0-preview.5.24307.10). Can repro it with sample project.

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It seems this may be due to a change in the runtime. We are currently investigating this and have some ideas of how we can at least mitigate it in the short term.

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I also experienced this issue, it propagated as a compiler error for the MAUI community toolkit, whilst compiling.

XC0009 No property, BindableProperty, or event found for "Content", or mismatching type between value and property.

<?xml version="1.0" encoding="utf-8" ?>
<toolkit:Popup xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
               xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
               xmlns:toolkit="http://schemas.microsoft.com/dotnet/2022/maui/toolkit"
               x:Class="MyTeamSafe.Views.ProgressPopup">
    <VerticalStackLayout HorizontalOptions="Center" VerticalOptions="Center" BackgroundColor="Purple">
        <ActivityIndicator IsRunning="True" />
        <Label Text="{Binding Message}" />
    </VerticalStackLayout>

</toolkit:Popup>

My temporary workaround was to switch the TargetFramework from

<TargetFrameworks>net9.0-android</TargetFrameworks>

to

<TargetFrameworks>net8.0-android</TargetFrameworks>

But I'm now installing dotnet SDK 9 preview 4 and referencing that from my global.json file to force my project to use preview 4 instead of preview 5

{
  "sdk": {
    "INFO": "From command line type  `dotnet --list-sdks` to get the list of installed dotnet SDKs",
    "version": "9.0.100-preview.4.24267.66"
  }
}

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XC0009 No property, BindableProperty, or event found for "Content", or mismatching type between value and property.

Could you try enclosing the VerticalStackLayout with an explicit Content property tag, which might work?

<toolkit:Popup.Content>
<!-- Everything in-betwen -->
</toolkit:Popup.Content>

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Could you try enclosing the VerticalStackLayout with an explicit Content property tag, which might work?

I'm sorry, but this doesn't fix it.

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This crude method works.

Define an intermediate base class and modify your Popups to inherit from it.

public class MauiPopup : Popup
{
    public override View? Content
    {
        get => base.Content;
        set => base.Content = value;
    }
}

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Another example of this:

https://learn.microsoft.com/en-us/dotnet/communitytoolkit/maui/views/expander

<mct:Expander>
    <mct:Expander.Header>
        <Label Text="Baboon"
               FontAttributes="Bold"
               FontSize="Medium" />
    </mct:Expander.Header>
    <HorizontalStackLayout Padding="10">
        <Image Source="http://upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Papio_anubis_%28Serengeti%2C_2009%29.jpg/200px-Papio_anubis_%28Serengeti%2C_2009%29.jpg"
               Aspect="AspectFill"
               HeightRequest="120"
               WidthRequest="120" />
        <Label Text="Baboons are African and Arabian Old World monkeys belonging to the genus Papio, part of the subfamily Cercopithecinae."
               FontAttributes="Italic" />
    </HorizontalStackLayout>
</mct:Expander>

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Tested 8.0.70-ci.net8.24320.1 and I'm no longer seeing the error. A result of #23031 being merged?

Nightly 9.0.0-preview.5.24307.10 still generates the error. In both cases building with net9.0-ios.

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