Design-time theme references in WPF Class Library without App.xaml

[thelusico]

Problem Description

We have a WPF class library project that loads Fluent Theme at runtime and faces challenges with view references. Our specific constraints are:

• Project Type: WPF Class Library (not executable)
• Host Environment: Called from WinForms applications
• Theme Loading: Fluent Theme loaded dynamically at runtime
• Constraint: Cannot use App.xaml since the WPF views are hosted by external WinForms projects

Current Challenge

We need a global solution to resolve theme references in our views without:

1. Having to modify every individual view
2. Relying on App.xaml (which doesn't work in our scenario)
3. Manual reference management across multiple views

What We've Tried

1. Fake App.xaml Approach: Created a fake App.xaml and attempted to exclude it from build, but Visual Studio ignores the configuration and always processes the App.xaml file.
2. Created a DesignTimeFluentTheme.xaml file containing all theme references for design-time support. Attempted to replace this file with a "blank" version during build using MSBuild targets in the .csproj, but this approach didn't work as expected.

Desired Solution

Looking for a "Fake App.xaml" equivalent that provides:

• Global theme resource registration
• Automatic resource resolution for all views
• No per-view modification required
• Compatible with class library architecture
• Works when hosted by external WinForms applications

What's the recommended approach for globally registering theme resources in a WPF class library that will be consumed by external applications? Are there alternatives to App.xaml that can provide similar resource resolution capabilities?

Any insights or workarounds would be greatly appreciated!

[lindexi]

My solution is add the code to csproj:

    <ApplicationDefinition Include="App_MakeReshaperHappy.xaml" Condition="false">
      <Generator>MSBuild:Compile</Generator>
      <SubType>Designer</SubType>
    </ApplicationDefinition>

And I create the fake App.xaml named App_MakeReshaperHappy.xaml. And which can make the Resharper happy.

You can find all my code in https://github.com/lindexi/lindexi_gd/tree/b771e3f0/HallnebubeaChelnawjecere