Application must be instantiated before call to window constructor due to resources in App.xaml

[cmeeren]

When using Program.runWindow, the window must necessarily be instantiated first. Since Application isn't instantiated before calling runWindow, I get the following exception on the InitializeComponent() call in the window constructor:

Exception: Cannot find resource named 'MaterialDesignMultiFloatingActionAccentPopupBox'. Resource names are case sensitive.

This error occurs because the resource in question is defined in my App.xaml:

<Application.Resources>
  <ResourceDictionary>
    <ResourceDictionary.MergedDictionaries>
      <ResourceDictionary Source="pack://application:,,,/MaterialDesignThemes.Wpf;component/Themes/MaterialDesignTheme.Light.xaml" />
      <ResourceDictionary Source="pack://application:,,,/MaterialDesignThemes.Wpf;component/Themes/MaterialDesignTheme.Defaults.xaml" />
      <ResourceDictionary Source="pack://application:,,,/MaterialDesignColors;component/Themes/Recommended/Primary/MaterialDesignColor.Blue.xaml" />
      <ResourceDictionary Source="pack://application:,,,/MaterialDesignColors;component/Themes/Recommended/Accent/MaterialDesignColor.Lime.xaml" />
      <ResourceDictionary Source="pack://application:,,,/MaterialDesignThemes.Wpf;component/Themes/MaterialDesignTheme.PopupBox.xaml" />
    </ResourceDictionary.MergedDictionaries>
  </ResourceDictionary>
</Application.Resources>

Since this is not instantiated/loaded before the window is initialized, I am unable to initialize my main window to start the app.

What is the best way to solve this? Is there something I can do, or must this be fixed in Elmish.WPF?

[cmeeren]

One workaround is of course to define the resources in all XAML files, but that's a horrible solution for obvious reasons. Surely there must be some way to use application-wide resources when using Elmish.WPF?

If this is indeed currently impossible, the fix could be as simple as adding a function runWithWindow that instead of a Window takes unit -> Window, and use this in Elmish.WPF.Program._run, and instantiate Application before instantiating the window. (Though if it's impossible to use resources in App.xaml with Elmish.WPF, I'd argue that this should be the default and only behavior and that runWindow should be changed.)

[cmeeren]

In fact, I see that Elmish.WPF calls Application() directly and doesn't use my custom Application subclass, which contains overrides for OnStartup etc. Is there any way to tell Elmish.WPF to use a custom Application class? If not, could this be implemented, and are there any other ways to do OnStartup and similar stuff?

[cmeeren]

Closed by #48