Trouble referencing a Resource Dictionary that contains a Merged Dictionary

Question

I have a library, CommonLibraryWpfThemes, with several Resource Dictionary XAML files in it. My Themes/Generic.xml file contains a ResourceDictionary.MergedDictionaries declaration that merges all the other files together.

Generic.xaml

<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"&gt;
    <ResourceDictionary.MergedDictionaries>
        <ResourceDictionary
            Source="/CommonLibraryWpfThemes;component/ResourceDictionaries/BrushDictionary.xaml" />
        <ResourceDictionary
            Source="/CommonLibraryWpfThemes;component/ResourceDictionaries/TextBlockDictionary.xaml" />
        <ResourceDictionary
            Source="/CommonLibraryWpfThemes;component/ResourceDictionaries/LabelDictionary.xaml" />
        <ResourceDictionary
            Source="/CommonLibraryWpfThemes;component/ResourceDictionaries/ButtonDictionary.xaml" />
        <ResourceDictionary
            Source="/CommonLibraryWpfThemes;component/ResourceDictionaries/WindowDictionary.xaml" />
    </ResourceDictionary.MergedDictionaries>
</ResourceDictionary>

In my application project, I have a reference to CommonLibraryWpfThemes, and I explicitly reference Generic.xml in my App.xaml file.

App.xaml -- FAILS

<Application
    x:Class="MyApp.App"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"&gt;
    <Application.Resources>
        <ResourceDictionary
            Source="/CommonLibraryWpfThemes;component/Themes/Generic.xaml" />
    </Application.Resources>
</Application>

This doesn't work. I get the following error when I run my app:

System.Windows.Markup.XamlParseException occurred
  Message="Cannot find resource named '{_fadedOrangeBrush}'. Resource names are case sensitive.  Error at object 'System.Windows.Setter' in markup file 'CommonLibraryWpfThemes;component/ResourceDictionaries/WindowDictionary.xaml' Line 18 Position 13."
  Source="PresentationFramework"
  LineNumber=18
  LinePosition=13

If I place the contents of Generic.xaml into App.xaml directly, everything works fine:

App.xaml -- SUCCEEDS

<Application
    x:Class="MyApp.App"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"&gt;
    <Application.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary
                    Source="/CommonLibraryWpfThemes;component/ResourceDictionaries/BrushDictionary.xaml" />
                <ResourceDictionary
                    Source="/CommonLibraryWpfThemes;component/ResourceDictionaries/TextBlockDictionary.xaml" />
                <ResourceDictionary
                    Source="/CommonLibraryWpfThemes;component/ResourceDictionaries/LabelDictionary.xaml" />
                <ResourceDictionary
                    Source="/CommonLibraryWpfThemes;component/ResourceDictionaries/ButtonDictionary.xaml" />
                <ResourceDictionary
                    Source="/CommonLibraryWpfThemes;component/ResourceDictionaries/WindowDictionary.xaml" />
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </Application.Resources>
</Application>

---

Maybe I'm going about this in the wrong way. My goal is to make it easy to reference all my theme resources from multiple applications without having to list out all the individual files. Is there a recommended way to do this? (Note: I'm not trying to switch between multiple themes--I just have one theme.)

As a bonus, it would be nice if someone could tell me how to reference resources in an external library without breaking the designer in Visual Studio.

Thanks.

EDIT:

I tried wrapping the ResourceDictionary in a ResourceDictionary.MergedDictionary element, but that also didn't work (I get the same error):

<Application
    x:Class="MyApp.App"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"&gt;
    <Application.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary
                    Source="/CommonLibraryWpfThemes;component/Themes/Generic.xaml" />
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </Application.Resources>
</Application>

Answer 1

You should not have to reference generic.xaml at all, it has built-in support. This however means that it provides default styling, which you do not set explicitly. Explicitly set styles/templates need to be attainable from explicitly referenced res dictionaries.

(EDIT for clarity)

One exception to this is the App.xaml, where defined resources become accessible by the whole app, without requiring to reference any specific resource dictionary. The resource itself, would have to be accessible by name.

The reason why this fails

<Application.Resources>
    <ResourceDictionary
        Source="/CommonLibraryWpfThemes;component/Themes/Generic.xaml" />
</Application.Resources>

is, I think, because you didn't wrap it in a MergedDictionary wrapper, adding it to merged dictionaries. Adding directly to resources works only for resources you declare locally, e.g. the styles, etc. themselves.

However, as I said before, you shouldn't have to merge generic.xaml anywhere, maybe you should just refactor brushes and other resources used outside styles, and merge only those resources in app.xaml.

Also note that styles do not have to be in generic.xaml to have "default style" behaviour - if a style with key equal to the type of the element is accessible to it (globally, or in local resources), then it will use the style as a default style. The generic.xaml is just a convenience.

Check this answer.

For other custom brushes, etc, you need to reference those resources explicitly.

You should also check the contents of the WindowDictionary.xaml, this error has a certain smell about it.

Answer 2

Check your constructor in App.xaml.cs calls InitializeComponent() - this is what merges the resource dictionaries...

Answer 3

I'm having the exact same issue. Basically I have an application that uses the System.AddIn.Pipeline namespace to allow us to add Class Libraries into the application.

Regardless of that Black Box - the class I am working with worked until I tried to rescale the ResourceDictionary of a control into a seperate Resource (FormattingResourceDictionary.xaml).

The problem is that the ResourceDictionary used Converters (e.g. BooleanToVisibilityConverter.cs) which was called by :BooleanToVisibilityConverter.

This now fails with the same message. The application resources are not applicable as they do not exist (no App.xaml) so what am I to do?

Answer 4

My solution is here

https://connect.microsoft.com/VisualStudio/feedback/details/609601/merge-dictionaries-does-not-work-when-we-merge-merged-dictionaries#tabs

Click workarounds