.NET 9: Runtime crashes when utilizing legacy libraries.

[daltzctr]

Description

MAUI class libraries that utilize the following features

• Obsoleted controls such as Frame
• Obsoleted APIs such as Device
• Missing datatypes (previously this would fall back to reflection based bindings)
• x:DataType={x:Object} which would previously fall back to reflection based bindings.

Will runtime crash when used in a consumer project. The consumer project has no warnings about any incompatibilities and will just crash.

Some examples of offending libraries are

• https://github.com/roubachof/Sharpnado.Tabs (utilizes Border and Device)
• https://github.com/akgulebubekir/Maui.DataGrid (version 4.0.4 or less) (missing datatypes and usage of x:DataType={x:Object}

Proposal:
I am not sure of the technical challenges on this, but it would be nice to either mark .NET 8 MAUI libraries with warnings as possibly incompatible, or detect incompatibilities in referenced libraries and throw a compile time error. This is no workaround and library maintainers must fix the issues by fixing the obsoleted references and ensure they are datatyping everything (replace x:DataType={x:Object} with x:DataType={x:Null} to explicitly opt in to reflection based bindings as a short term workaround.

Steps to Reproduce

1. Create a new MAUI project
2. Include the Maui.DataGrid (https://github.com/akgulebubekir/Maui.DataGrid) nuget
3. Add a reference to datagrid in XAML, no need to add itemsource
4. Build.
   • Observe no warnings at compile time
5. Run the application. It will throw an exception that points to some Xaml activator and in Android, points to the datagrid library.

Link to public reproduction project repository

No response

Version with bug

9.0.0-rc.1.24453.9

Is this a regression from previous behavior?

Yes, this used to work in .NET MAUI

Last version that worked well

8.0.82 SR8.2

Affected platforms

iOS, Android

Affected platform versions

No response

Did you find any workaround?

No. The only workaround has been to fix the references upstream.

Relevant log output

No response

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[jonathanpeppers]

@daltzctr can you share the stack trace of some of these crashes?

Do we know if this change was in RC 1, it was merged only 2 weeks ago, so perhaps not:

• [XC] Fallback to reflection-based bindings for bindings with "invalid" path #24238

The idea is it should restore a lot of previous behavior from .NET 8.

[jonathanpeppers]

No, I don't see it in RC 1:

• https://github.com/dotnet/maui/commits/release/9.0.1xx-rc1?author=simonrozsival

[daltzctr]

@jonathanpeppers

Sharpnado (obsolete references, so not datatype related)

Unhandled managed exception: Exception has been thrown by the target of an invocation. (System.Reflection.TargetInvocationException)
   at System.Reflection.MethodBaseInvoker.InvokeWithNoArgs(Object obj, BindingFlags invokeAttr)
   at System.RuntimeType.CreateInstanceMono(Boolean nonPublic, Boolean wrapExceptions)
   at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean wrapExceptions)
   at System.Activator.CreateInstance(Type type, Boolean nonPublic, Boolean wrapExceptions)
   at System.Activator.CreateInstance(Type type, Boolean nonPublic)
   at System.Activator.CreateInstance(Type type)
   at Microsoft.Maui.Controls.Xaml.CreateValuesVisitor.Visit(ElementNode node, INode parentNode)
   at Microsoft.Maui.Controls.Xaml.ElementNode.Accept(IXamlNodeVisitor visitor, INode parentNode)
   at Microsoft.Maui.Controls.Xaml.ApplyPropertiesVisitor.<>c__DisplayClass43_0.<SetTemplate>b__0()
   at Microsoft.Maui.Controls.ElementTemplate.CreateContent()
at Sharpnado.Tabs.TabHostView.CreateTabItem(Object item)
   at Sharpnado.Tabs.TabHostView.InitializeItems()
   at Sharpnado.Tabs.TabHostView.UpdateItemsSource()
   at Sharpnado.Tabs.TabHostView.OnPropertyChanged(String propertyName)
   at Microsoft.Maui.Controls.BindableObject.OnBindablePropertySet(BindableProperty property, Object original, Object value, Boolean didChange, Boolean willFirePropertyChanged)

Maui.DataGrid (x:Object and missing DataTypes)

[0:] [13:46:57 FTL] Inner Exception: 
 System.NullReferenceException: Object reference not set to an instance of an object.
   at Microsoft.Maui.Controls.Xaml.BindingExtension.<Microsoft.Maui.Controls.Xaml.IMarkupExtension<Microsoft.Maui.Controls.BindingBase>.ProvideValue>g__CreateBinding|40_0(<>c__DisplayClass40_0& ) in /_/src/Controls/src/Xaml/MarkupExtensions/BindingExtension.cs:line 46
   at Microsoft.Maui.Controls.Xaml.BindingExtension.Microsoft.Maui.Controls.Xaml.IMarkupExtension<Microsoft.Maui.Controls.BindingBase>.ProvideValue(IServiceProvider serviceProvider) in /_/src/Controls/src/Xaml/MarkupExtensions/BindingExtension.cs:line 27
   at Maui.DataGrid.DataGrid.InitializeComponent() in D:\Maui.DataGrid\Maui.DataGrid\Microsoft.Maui.Controls.SourceGen\Microsoft.Maui.Controls.SourceGen.CodeBehindGenerator\DataGrid.xaml.sg.cs:line 53
   at Maui.DataGrid.DataGrid..ctor() in D:\Maui.DataGrid\Maui.DataGrid\DataGrid.xaml.cs:line 46
   at System.Reflection.MethodBaseInvoker.InterpretedInvoke_Constructor(Object obj, IntPtr* args)
   at System.Reflection.MethodBaseInvoker.InvokeWithNoArgs(Object obj, BindingFlags invokeAttr)

[jonathanpeppers]

@daltzctr this should hopefully fix Maui.DataGrid:

• [xaml] fix potential NRE in {Binding} #24756

For Sharpnado.Tabs that could be a different issue, do you have a sample showing the problem?

[jonathanpeppers]

I believe this also would fix Sharpnado.Tabs, checking InitializeComponent() of BottomTabItem, I see the same issue:

But if @daltzctr has a sample, I could test for sure. Closing, thanks!