Global style in a separate assembly - wpf

Question

For my application themes, I created a separate class library MyApp.Themes.dll.
In the root folder of this library I have Standard.xaml:
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary
Source="pack://application:,,,/MyApp.Themes;component/Standard/Accordion.xaml"/>
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
In Standard folder I have Accordion.xaml:
<ResourceDictionary xmlns:layoutPrimitivesToolkit="..."
xmlns:layoutToolkit="..."
...>
<!-- layoutPrimitivesToolkit:AccordionButton -->
<Style TargetType="layoutPrimitivesToolkit:AccordionButton">
...
</Style>
...
</ResourceDictionary>
which are default styles for WPF Toolkit Accordion control, except that style for
AccordionItem is modified to set background to transparent (instead of blue, which is a known bug).
For both xaml files Build Action is set to "Resource".
Now, after referencing MyApp.Themes library in MyApp WPF project, in App.xaml I wrote the following:
<Application.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary
Source="pack://application:,,,/MyApp.Themes;component/Standard.xaml" />
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Application.Resources>
It doesn't work (no error; just style not applied). If I copy&paste Accordion.xaml styles directly in App.xaml, then it works.
Some people suggested adding dummy resource dictionary, so I added the following in App.xaml after MergedDictionaries ending tag:
<Style TargetType="{x:Type layoutToolkit:AccordionItem}" />
Again, it doesn't work. Can someone help me solve this? By the way, I didn't try an approach
suggested by some others - using basedOn. If I must do that, I'd like to do in MyApp.Themes,
because it makes using themes nicer in App.xaml. Thank you in advance.
UPDATE1: It works if I directly copy&paste Accordion.xaml content to Standard.xaml
UPDATE2: I tried local assembly resource file URI (http://msdn.microsoft.com/en-us/library/aa970069.aspx) in Standard.xaml:
<ResourceDictionary Source="pack://application:,,,/Standard/Accordion.xaml"/>
It throws an error, saying standard/accordion.xaml not found.

Answer 1

It seems there's a bug in .NET. See the thread below:
Trouble referencing a Resource Dictionary that contains a Merged Dictionary
Also, there's a connect page on Microsoft site:
https://connect.microsoft.com/VisualStudio/feedback/details/609601/merge-dictionaries-does-not-work-when-we-merge-merged-dictionaries#tabs