Mah apps resource not found in a wpf class library

Question

My application is using a wpf library (uilib.vcproj) which itself uses another ( corelib.vcproj).

In coreLib a resource dictionary (MahAppsMetroStyles.xaml) exist whic define mah app style and it s in app.xaml through

 <Application.Resources>
     <ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
         <ResourceDictionary.MergedDictionaries>

             <ResourceDictionary Source="pack://application:,,,/corelib;component/Resources/MahAppsMetroStyles.xaml" />
         </ResourceDictionary.MergedDictionaries>
     </ResourceDictionary>
 </Application.Resources>

but in uilib and corelib controls MahApps is unknown until i run the application. Resource not found

On my "english" computer it works in uilib , on the french one nothing works, all controls look ugly

I rebuilt, closed visual studio, create a MahAppsMetroStyles partial class inheriting from resource dictionary