OnlineMonitorSystem/HandyControl/HandyControl_Shared/Themes/Styles/Expander.xaml

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

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

    <Style x:Key="Expander.Small" BasedOn="{StaticResource ExpanderBaseStyle}" TargetType="Expander">
        <Setter Property="MinHeight" Value="20" />
        <Setter Property="MinWidth" Value="20" />
    </Style>

</ResourceDictionary>