Segmented Control in WPF XAML ISLAND, XAML parsing failed.

[TekuSP]

Describe the bug

Hello,

When I add xmlns:controls="using:CommunityToolkit.WinUI.Controls" And

<controls:Segmented>
    
</controls:Segmented> 

To StackPanel, the Window does not initialize anymore with cryptic error: XAML parsing failed.

I think the issue is how I initialize resources:

protected override void OnLaunched(Microsoft.UI.Xaml.LaunchActivatedEventArgs args)
{
    XamlControlsXamlMetaDataProvider.Initialize();
    xamlMetaDataProvider = new();
    this.Resources.MergedDictionaries.Add(new Microsoft.UI.Xaml.Controls.XamlControlsResources());
    //this.Resources.MergedDictionaries.Add(new Microsoft.UI.Xaml.ResourceDictionary() { Source = new Uri("ms-appx:///CommunityToolkit.WinUI.Controls.Segmented/Themes/Generic.xaml") });

}

If I uncomment my attempt to load Segmented, it fails on COM Exception.

Steps to reproduce

https://github.com/castorix/WPF_XAML_Islands_WinUI3/tree/master

Clone this repo, update to newest WinUI SDK, add CommunityToolkit.WinUI.Segmented and add Segmented. Same issue.

Expected behavior

Segmented loads?

Screenshots

No response

Code Platform

• [ ] UWP
• [x] WinAppSDK / WinUI 3
• [ ] Web Assembly (WASM)
• [ ] Android
• [ ] iOS
• [ ] MacOS
• [ ] Linux / GTK

Windows Build Number

• [ ] Windows 10 1809 (Build 17763)
• [ ] Windows 10 1903 (Build 18362)
• [ ] Windows 10 1909 (Build 18363)
• [ ] Windows 10 2004 (Build 19041)
• [ ] Windows 10 20H2 (Build 19042)
• [ ] Windows 10 21H1 (Build 19043)
• [ ] Windows 10 21H2 (Build 19044)
• [x] Windows 10 22H2 (Build 19045)
• [ ] Windows 11 21H2 (Build 22000)
• [ ] Other (specify)

Other Windows Build number

No response

App minimum and target SDK version

• [ ] Windows 10, version 1809 (Build 17763)
• [ ] Windows 10, version 1903 (Build 18362)
• [ ] Windows 10, version 1909 (Build 18363)
• [x] Windows 10, version 2004 (Build 19041)
• [ ] Windows 10, version 2104 (Build 20348)
• [ ] Windows 11, version 22H2 (Build 22000)
• [ ] Other (specify)

Other SDK version

No response

Visual Studio Version

No response

Visual Studio Build Number

2026 Version: 18.0.0

Device form factor

Desktop

Additional context

It is WPF XAML ISLANDS.

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