the line ResourceDictionary Source="..." ist underlined and the VS designer throws an Exception. Everything was working in VS 2008
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="pack://application:,,,/MySolution.MyProject;component/Styles/MyStyles.xaml" />
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
Exception:
Exception:Value cannot be null. Parameter name: item (Same for the InnerException)
at Microsoft.Expression.Platform.InstanceBuilders.ClrObjectInstanceBuilder.InstantiateChildren(IInstanceBuilderContext context, ViewNode viewNode, DocumentCompositeNode compositeNode, Boolean isNewInstance)