[Bug]: Adding DevWinUI components to a project

[ian-mcpherson]

Describe the bug

I have a fresh install of Visual Studio Community ver: 18.4.0. After adding the DevWinUI extension and creating a new solution. When adding DevWinUI specific components I get the following error. from Visual Studio.

The given key was not present in the dictionary.

Steps to reproduce the bug

1. Add New Item
2. Select WinUI
3. Select Blank Page and rename as required
4. Click Add.
5. Creates the .xaml but not the code behind .cs file
6. Reports the error: The given key was not present in the dictionary.

Expected behavior

Previos editions I did not have this issue.

Screenshots

No response

NuGet package version

DevWinUI 9.5.0

IDE

Visual Studio 2026

Additional context

No response