XamlC error XFC0045 with maui dotnet 9 preview 3 about maui HOT 15 OPEN

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Closed similar issues:

• XamlC compiler null-refs when encountering a binding to an array access (#10396), similarity score: 0.71
• Resolving an x:Reference in a RELEASE build picks the wrong element in some cases. (#8149), similarity score: 0.71
• XamlC XC0022 error : Binding could be compiled if x:DataType is specified. (#20568), similarity score: 0.71
• [regression/8.0.0-preview.1.7762] [WinUI] CollectionView runtime binding errors when loading the ItemSource asynchronously (#16787), similarity score: 0.70
• The "XamlCTask" task failed unexpectedly. (#21910), similarity score: 0.70

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from maui.

The same error if you use
SelectionChangedCommandParameter="{Binding Source={RelativeSource Self}, Path=SelectedItem}"

from maui.

Verified this issue with Visual Studio 17.10 Preview 7.0 + NET9.0 SDK (9.0.100-preview.3.24204.13).
MauiVersion = 9.0.0-preview.3.10457, repro this issue;
MauiVersion = 9.0.0-preview.2.10293, works well.

from maui.

Hi guys, I am facing these issues as well. Is there any workaround settings where we can bypass the error from XamlC

similar to
<XFDisableTargetsValidation>True</XFDisableTargetsValidation>

cos right now, I can't build and compile the project. kindly advise.

from maui.

There's been a few changes in SetPropertiesVisitor since Preview2, and I think this is the only place that throws that exception: https://github.com/dotnet/maui/blame/main/src/Controls/src/Build.Tasks/SetPropertiesVisitor.cs

@simonrozsival Would you have any ideas what it could be?

from maui.

@rogerbriggen @drasticactions previously, any binding with Source wasn't compiled. After a recent change (#20610), we can now compile all bindings. Unfortunately, we can't infer the x:DataType form Source yet (#21834) and so in this case, the compiler doesn't know that it shouldn't be looking for the property SelectedItem on MainPageViewModel but instead on CollectionView.

As a fix, you can set the x:DataType on the binding that shouldn't inherit the parent's x:DataType:

<CollectionView 
    x:Name="myCollection" 
    ItemsSource="{Binding Items}" 
    ...
    SelectionChangedCommandParameter="{Binding Source={x:Reference myCollection}, Path=SelectedItem, x:DataType=CollectionView}">
    <CollectionView.ItemTemplate>
     ...
    </CollectionView.ItemTemplate>
</CollectionView>

Does this solve your problem?

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one thing I found out is that when any parent element has assigned the x Attribute x:DataType with value, those child elements will be overriding with the parent value... basically, it is using the parent context to find the binding hence it throws the Property Binding not found.

from maui.

@rogerbriggen @drasticactions previously, any binding with Source wasn't compiled. After a recent change (#20610), we can now compile all bindings. Unfortunately, we can't infer the x:DataType form Source yet (#21834) and so in this case, the compiler doesn't know that it shouldn't be looking for the property SelectedItem on MainPageViewModel but instead on CollectionView.

As a fix, you can set the x:DataType on the binding that shouldn't inherit the parent's x:DataType:

<CollectionView 
    x:Name="myCollection" 
    ItemsSource="{Binding Items}" 
    ...
    SelectionChangedCommandParameter="{Binding Source={x:Reference myCollection}, Path=SelectedItem, x:DataType=CollectionView}">
    <CollectionView.ItemTemplate>
     ...
    </CollectionView.ItemTemplate>
</CollectionView>

Does this solve your problem?
Many thanks for the response. Seem like I just need to remove the x:DataType for the time being.

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@simonrozsival Okay, that makes sense. Should this issue be closed then and duplicated under #21834?

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@drasticactions I'm not sure. I think this is mostly a documentation issue. We've made changes to how XamlC compiles bindings in .NET 9, but we haven't updated the docs yet. I think we need a new issue that will track the necessary changes to documentation and then we can close this issue.

from maui.

@rogerbriggen @drasticactions previously, any binding with Source wasn't compiled. After a recent change (#20610), we can now compile all bindings. Unfortunately, we can't infer the x:DataType form Source yet (#21834) and so in this case, the compiler doesn't know that it shouldn't be looking for the property SelectedItem on MainPageViewModel but instead on CollectionView.

As a fix, you can set the x:DataType on the binding that shouldn't inherit the parent's x:DataType:

<CollectionView 
    x:Name="myCollection" 
    ItemsSource="{Binding Items}" 
    ...
    SelectionChangedCommandParameter="{Binding Source={x:Reference myCollection}, Path=SelectedItem, x:DataType=CollectionView}">
    <CollectionView.ItemTemplate>
     ...
    </CollectionView.ItemTemplate>
</CollectionView>

Does this solve your problem?

@cgp1976 Yes, this solves this issue. The only thing which is, that Visual Studio shows an error

The text means "the datatype property was not found in type BindingExtension.
Do I need to create a bug for that? Where?

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@rogerbriggen I think this is the same warning we saw in #21434. This seems to be a bug in the XAML editor in VS. I wonder where the best place to report it is (cc @StephaneDelcroix @PureWeen).

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@mgoertz-msft Would you know?

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Xamarin and MAUI never cease to surprise me on what they allow that other platforms like WPF and UWP/WinUI don't. I had no idea this was allowed to be used that way.

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I reported the issue in the VS Code extension here: microsoft/vscode-dotnettools#1131

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