.NET10-rc1 - XamlSourceGen - Partial method XXX.InitializeComponent()' must have an implementation part because it has accessibility modifiers.

[bcaceiro]

Description

Using the latest .NET10-rc1 , and trying out the xaml source gen in a new .net MAUI app, I have these errors:

Severity	Code	Description	Project	File	Line	Suppression State
Error (active)	CS8795	Partial method '__Type08BAD333D93A1098.InitializeComponent()' must have an implementation part because it has accessibility modifiers.	Maui10Preview7 (net10.0-android)	C:\P\net9-repros\Maui10Preview7\obj\Debug\net10.0-android\Microsoft.Maui.Controls.SourceGen\Microsoft.Maui.Controls.SourceGen.CodeBehindGenerator\Resources_Styles_Colors.xaml.sg.cs	26	

Severity	Code	Description	Project	File	Line	Suppression State
Error (active)	CS8795	Partial method '__Type3F0379CBCFA4A406.InitializeComponent()' must have an implementation part because it has accessibility modifiers.	Maui10Preview7 (net10.0-android)	C:\P\net9-repros\Maui10Preview7\obj\Debug\net10.0-android\Microsoft.Maui.Controls.SourceGen\Microsoft.Maui.Controls.SourceGen.CodeBehindGenerator\Resources_Styles_Styles.xaml.sg.cs	26	

where the culprits are the Colors.xml files and Styles.xml files ( default )

In order to enable the source gen I applied this:

<MauiXamlInflator>SourceGen</MauiXamlInflator>

On my .csproj

Steps to Reproduce

1. Clone https://github.com/bcaceiro/net9-repros/tree/main/Maui10Preview7
2. Build
3. See errors

Link to public reproduction project repository

https://github.com/bcaceiro/net9-repros/tree/main/Maui10Preview7

Version with bug

10.0.0-rc.1

Is this a regression from previous behavior?

Not sure, did not test other versions

Last version that worked well

Unknown/Other

Affected platforms

Android

Affected platform versions

No response

Did you find any workaround?

Not using the feature :)))))

Relevant log output

1>------ Build started: Project: Maui10Preview7, Configuration: Debug Any CPU ------
1>C:\Program Files\dotnet\sdk\10.0.100-rc.1.25451.107\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.RuntimeIdentifierInference.targets(345,5): message NETSDK1057: You are using a preview version of .NET. See: https://aka.ms/dotnet-support-policy
1>Skipping analyzers to speed up the build. You can execute 'Build' or 'Rebuild' command to run analyzers.
1>Including assemblies for Hot Reload support
1>C:\P\net9-repros\Maui10Preview7\obj\Debug\net10.0-android\Microsoft.Maui.Controls.SourceGen\Microsoft.Maui.Controls.SourceGen.CodeBehindGenerator\Resources_Styles_Colors.xaml.sg.cs(26,24,26,43): error CS8795: Partial method '__Type08BAD333D93A1098.InitializeComponent()' must have an implementation part because it has accessibility modifiers.
1>C:\P\net9-repros\Maui10Preview7\obj\Debug\net10.0-android\Microsoft.Maui.Controls.SourceGen\Microsoft.Maui.Controls.SourceGen.CodeBehindGenerator\Resources_Styles_Styles.xaml.sg.cs(26,24,26,43): error CS8795: Partial method '__Type3F0379CBCFA4A406.InitializeComponent()' must have an implementation part because it has accessibility modifiers.
1>Done building project "Maui10Preview7.csproj" -- FAILED.

[jfversluis]

This is probably some error in the XAML or a scenario in the XAML that is not generated correctly. Are you by any chance able to test the artifacts from this build (following these instructions, skip the GitHub part) when it completes?

That should have a lot more fixes for Source Gen that are coming in RC2 which might already fix this issue, and let us know please!

[bcaceiro]

This is probably some error in the XAML or a scenario in the XAML that is not generated correctly. Are you by any chance able to test the artifacts from this build (following these instructions, skip the GitHub part) when it completes?

That should have a lot more fixes for Source Gen that are coming in RC2 which might already fix this issue, and let us know please!

This is the default .net maui template app btw!

I will give it another try, last time I really couldn't get that local testing working, let's see if VS2026 will be better 💃

[bcaceiro]

@jfversluis I have finally instaled the CI build!

FYI - the instructions may not be clear - since my issue the last time was: I was clicking the VS tab: Updates for Packages, and it never picked up newer updates - however searching manually the MAUI package, it showed the CI local nuget build :)

Nevertheless - the issue still occurs with that build:

<PackageReference Include="Microsoft.Maui.Controls" Version="10.0.0-ci.net10.25461.35" />

1>C:\P\net9-repros\Maui10Preview7\obj\Debug\net10.0-android\Microsoft.Maui.Controls.SourceGen\Microsoft.Maui.Controls.SourceGen.CodeBehindGenerator\Resources_StylesColors.xaml.sg.cs(22,24,22,43): error CS8795: Partial method '__Type08BAD333D93A1098.InitializeComponent()' must have an implementation part because it has accessibility modifiers.
1>C:\P\net9-repros\Maui10Preview7\obj\Debug\net10.0-android\Microsoft.Maui.Controls.SourceGen\Microsoft.Maui.Controls.SourceGen.CodeBehindGenerator\Resources_StylesStyles.xaml.sg.cs(22,24,22,43): error CS8795: Partial method '__Type3F0379CBCFA4A406.InitializeComponent()' must have an implementation part because it has accessibility modifiers.
1>Done building project "Maui10Preview7.csproj" -- FAILED.

[StephaneDelcroix]

I can not repro, on -rc1, on my machine. I suspect something being handled differently on windows, as I have a test related to that failing

[bcaceiro]

I can not repro, on -rc1, on my machine. I suspect something being handled differently on windows, as I have a test related to that failing

I can confirm I am using Windows, with VS2026