WinUI3 Trying to change theme to dark throws exception Exception thrown: 'System.NotSupportedException' in WinRT.Runtime.dll An exception of type 'System.NotSupportedException' occurred in WinRT.Runtime.dll but was not handled in user code Specified method is not supported.

[cconner100]

Current behavior

Using the standard Visual studio template i inserted this line in the App.cs startup after
Host = await builder.NavigateAsync();
App.Current.RequestedTheme = ApplicationTheme.Dark;
Throws the exception
Exception thrown: 'System.NotSupportedException' in WinRT.Runtime.dll
An exception of type 'System.NotSupportedException' occurred in WinRT.Runtime.dll but was not handled in user code
Specified method is not supported.

Simple example located at https://github.com/cconner100/ChangeThemeToDark

In general it seems like anything i try to do in WinUI3 now throws exceptions

Here is my environment. I rebuilt my windows box, reinstalled VS2022 and Uno check.

Microsoft Visual Studio Enterprise 2022
Version 17.5.5
VisualStudio.17.Release/17.5.5+33627.172
Microsoft .NET Framework
Version 4.8.09032

Installed Version: Enterprise

Architecture Diagrams and Analysis Tools   00476-80000-00000-AA735
Microsoft Architecture Diagrams and Analysis Tools

Visual C++ 2022   00476-80000-00000-AA735
Microsoft Visual C++ 2022

ADL Tools Service Provider   1.0
This package contains services used by Data Lake tools

ASA Service Provider   1.0

ASP.NET and Web Tools   17.5.320.55692
ASP.NET and Web Tools

Azure App Service Tools v3.0.0   17.5.320.55692
Azure App Service Tools v3.0.0

Azure Data Lake Tools for Visual Studio   2.6.5000.0
Microsoft Azure Data Lake Tools for Visual Studio

Azure Functions and Web Jobs Tools   17.5.320.55692
Azure Functions and Web Jobs Tools

Azure Stream Analytics Tools for Visual Studio   2.6.5000.0
Microsoft Azure Stream Analytics Tools for Visual Studio

C# Tools   4.5.2-3.23171.7+d17f741546fad2786cbd6394d08619544e53a36d
C# components used in the IDE. Depending on your project type and settings, a different version of the compiler may be used.

Common Azure Tools   1.10
Provides common services for use by Azure Mobile Services and Microsoft Azure Tools.

Cookiecutter   17.0.22336.2
Provides tools for finding, instantiating and customizing templates in cookiecutter format.

Extensibility Message Bus   1.4.3 (main@2a4517a)
Provides common messaging-based MEF services for loosely coupled Visual Studio extension components communication and integration.

GitHub Copilot   1.82.1.0 (v1.82.1.0@10c323cc0)
GitHub Copilot is an AI pair programmer that helps you write code faster and with less work.

GitHub Copilot Agent   1.82.15 (v1.82.0)

Microsoft Azure Hive Query Language Service   2.6.5000.0
Language service for Hive query

Microsoft Azure Stream Analytics Language Service   2.6.5000.0
Language service for Azure Stream Analytics

Microsoft Azure Tools for Visual Studio   2.9
Support for Azure Cloud Services projects

Microsoft JVM Debugger   1.0
Provides support for connecting the Visual Studio debugger to JDWP compatible Java Virtual Machines

Mono Debugging for Visual Studio   17.5.9 (11975e6)
Support for debugging Mono processes with Visual Studio.

NuGet Package Manager   6.5.0
NuGet Package Manager in Visual Studio. For more information about NuGet, visit https://docs.nuget.org/

Python - Django support   17.0.22336.2
Provides templates and integration for the Django web framework.

Python - Profiling support   17.0.22336.2
Profiling support for Python projects.

Python with Pylance   17.0.22336.2
Provides IntelliSense, projects, templates, debugging, interactive windows, and other support for Python developers.

Razor (ASP.NET Core)   17.5.2.2316603+9f1b6856460af1e592d387ebef416eadddac453f
Provides languages services for ASP.NET Core Razor.

SQL Server Data Tools   17.2.40120.0
Microsoft SQL Server Data Tools

Test Adapter for Boost.Test   1.0
Enables Visual Studio's testing tools with unit tests written for Boost.Test.  The use terms and Third Party Notices are available in the extension installation directory.

Test Adapter for Google Test   1.0
Enables Visual Studio's testing tools with unit tests written for Google Test.  The use terms and Third Party Notices are available in the extension installation directory.

ToolWindowHostedEditor   1.0
Hosting json editor into a tool window

TypeScript Tools   17.0.20105.2003
TypeScript Tools for Microsoft Visual Studio

Uno Platform Extension   1.0
Uno Platform Extension to create cross-platform apps using iOS, Android, mac Catalyst, Skia and WebAssembly.

Visual Basic Tools   4.5.2-3.23171.7+d17f741546fad2786cbd6394d08619544e53a36d
Visual Basic components used in the IDE. Depending on your project type and settings, a different version of the compiler may be used.

Visual F# Tools   17.5.0-beta.23053.5+794b7c259d9646a7eb685dad865aa27da7940a21
Microsoft Visual F# Tools

Visual Studio IntelliCode   2.2
AI-assisted development for Visual Studio.

VisualStudio.DeviceLog   1.0
Information about my package

VisualStudio.Mac   1.0
Mac Extension for Visual Studio

VSPackage Extension   1.0
VSPackage Visual Studio Extension Detailed Info

Xamarin   17.5.0.173 (d17-5@33e727c)
Visual Studio extension to enable development for Xamarin.iOS and Xamarin.Android.

Xamarin Designer   17.5.3.46 (remotes/origin/d17-5@e4dd80b2bb)
Visual Studio extension to enable Xamarin Designer tools in Visual Studio.

Xamarin Templates   17.5.41 (ba80d05)
Templates for building iOS, Android, and Windows apps with Xamarin and Xamarin.Forms.

Xamarin.Android SDK   13.2.0.0 (d17-5/797e2e1)
Xamarin.Android Reference Assemblies and MSBuild support.
    Mono: 6dd9def
    Java.Interop: xamarin/java.interop/main@149d70fe
    SQLite: xamarin/sqlite/3.40.0@fdc1e34
    Xamarin.Android Tools: xamarin/xamarin-android-tools/main@9f02d77


Xamarin.iOS and Xamarin.Mac SDK   16.2.0.5 (7738c90c9)
Xamarin.iOS and Xamarin.Mac Reference Assemblies and MSBuild support.

Expected behavior

Should not throw exception and should change the theme to dark mode

[cconner100]

OK so not an UNO issue, its an issue with WinUI3, see https://stackoverflow.com/questions/34554871/changing-theme-in-windows-10-uwp-app-programmatically

Question to the Uno gang. Do you have a solution for this that is cross platform? While i can implement this on WinUI3 i get all sorts of issues with iOS and Net7.0

thanks

Stack Overflow

Changing Theme in Windows 10 UWP App Programmatically

I was able to change theme using this.RequestedTheme = ElementTheme.Dark; But what I need is the whole application level, since this one only change the theme of the current page to dark.

Whenever...

[MartinZikmund]

You can switch app level theme in the constructor at launch or switch the theme of root element at runtime, but theming individual regions of the app (element-level theming) is not supported yet (although the recent changes will make this easier to achieve soon). Uno.Extensions offer ThemeService which makes switching themes much easier.

[nickrandolph]

There are also the SystemThemeHelper class in Toolkit that is quite useful - https://github.com/unoplatform/uno.toolkit.ui/blob/main/src/Uno.Toolkit.UI/Helpers/SystemThemeHelper.cs

[cconner100]

Thanks for the help guys