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

    <ResourceDictionary.MergedDictionaries>
        <ResourceDictionary Source="Base/ExpanderBaseStyle.xaml"/>
    </ResourceDictionary.MergedDictionaries>

    <Style BasedOn="{StaticResource ExpanderBaseStyle}" TargetType="Expander"/>

</ResourceDictionary>