WPF Fluent stopped working after I updated Visual Studio (and .NET SDK)

[TonyHenrique]

Description

I was using a recent feature of WPF that is this Fluent Resource, using this:

<ResourceDictionary Source="pack://application:,,,/PresentationFramework.Fluent;component/Resources/Fluent.xaml" />

But after I updated Visual Studio, this resource is not being found and a new build of the App is not running anymore.

Reproduction Steps

Create a new WPF Application, and use the resource dictionary like this example:

<Application x:Class="SubtitlesToSpeech.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:local="clr-namespace:SubtitlesToSpeech"
             StartupUri="MainWindow.xaml">
    <Application.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary Source="pack://application:,,,/PresentationFramework.Fluent;component/Resources/Fluent.xaml" />
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </Application.Resources>
</Application>

Expected behavior

The App runs with the fluent, with the provided code. (Perhaps something changed and I am not aware?)

Actual behavior

It is giving this exception when I run the app, (that was working before I update the VS and .NET SDK)

System.Windows.Markup.XamlParseException: ''Set property 'System.Windows.ResourceDictionary.Source' threw an exception.' Line number '9' and line position '18'.'


Inner Exception
IOException: Cannot locate resource 'resources/fluent.xaml'.

This exception was originally thrown at this call stack:
    MS.Internal.AppModel.ResourcePart.GetStreamCore(System.IO.FileMode, System.IO.FileAccess)
    System.IO.Packaging.PackagePart.GetStream(System.IO.FileMode, System.IO.FileAccess)
    MS.Internal.IO.Packaging.PackagePartExtensions.GetSeekableStream(System.IO.Packaging.PackagePart, System.IO.FileMode, System.IO.FileAccess)
    System.IO.Packaging.PackWebResponse.CachedResponse.GetResponseStream()
    System.IO.Packaging.PackWebResponse.ContentType.get()
    MS.Internal.WpfWebRequestHelper.GetContentType(System.Net.WebResponse)
    MS.Internal.WpfWebRequestHelper.GetResponseStream(System.Net.WebRequest, out MS.Internal.ContentType)
    System.Windows.ResourceDictionary.Source.set(System.Uri)
    MS.Internal.Xaml.Runtime.ClrObjectRuntime.SetValue(object, System.Xaml.XamlMember, object)

Regression?

It was working on previous preview.
After I updated visual studio to Version 17.12.0 Preview 1.0 , dotnet SDK 9.0.100-preview.7.24407.12
It stopped working.

Known Workarounds

No response

Impact

No response

Configuration

No response

Other information

No response

[h3xds1nz]

The path has changed, it is already reflected in the documentation, however to fix it change it to:

pack://application:,,,/PresentationFramework.Fluent;component/Themes/Fluent.xaml

[TonyHenrique]

Changed it here and worked!
Thank you @h3xds1nz !

[Slluxx]

pack://application:,,,/PresentationFramework.Fluent;component/Themes/Fluent.xaml

It would be nice to provide a link to the page that talks about this. This may be obvious to people working with the project but for a newcomer trying net9 and wpf for the first time, all the kinds of different docs for all the different UI systems are extremely confusing.