PDFOffice_Windows_exe/PDF Office/Styles/ExpanderStyle.xaml

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

    <Style x:Key="ExpanderDownHeaderStyle" TargetType="{x:Type ToggleButton}">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type ToggleButton}">
                    <Border Padding="{TemplateBinding Padding}">
                        <Grid Background="Transparent" SnapsToDevicePixels="False">
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="auto"/>
                                <ColumnDefinition Width="19"/>
                            </Grid.ColumnDefinitions>
                            <Path x:Name="arrow" Visibility="Collapsed" Grid.Column="1" Data="M4 5.00023L8.00012 0.000115851H-0.000115851L4 5.00023Z" HorizontalAlignment="Center" Fill="#8F96A7" SnapsToDevicePixels="false" VerticalAlignment="Center"/>
                            <Path x:Name="arrow2"  Grid.Column="1" Data="M5.00023 4L0.000115514 -0.000116188L0.000116188 8.00012L5.00023 4Z" HorizontalAlignment="Center" Fill="#8F96A7" SnapsToDevicePixels="false" VerticalAlignment="Center"/>
                            <ContentPresenter  HorizontalAlignment="Left" Margin="4,0,0,0" RecognizesAccessKey="True" SnapsToDevicePixels="True" VerticalAlignment="Center"/>

                        </Grid>
                    </Border>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsChecked" Value="true">
                            <Setter Property="Visibility" TargetName="arrow" Value="Visible"/>
                            <Setter Property="Visibility" TargetName="arrow2" Value="Collapsed"/>
                        </Trigger>

                        <Trigger Property="IsMouseOver" Value="true">
                        </Trigger>
                        <Trigger Property="IsPressed" Value="true">

                        </Trigger>
                        <Trigger Property="IsEnabled" Value="false">

                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

    <Style x:Key="PromotionExpanderStyle" TargetType="{x:Type Expander}">
        <Setter Property="Background" Value="Transparent"/>
        <Setter Property="HorizontalContentAlignment" Value="Stretch"/>
        <Setter Property="VerticalContentAlignment" Value="Stretch"/>
        <Setter Property="BorderBrush" Value="Transparent"/>
        <Setter Property="BorderThickness" Value="1"/>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type Expander}">
                    <Border Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" CornerRadius="3" SnapsToDevicePixels="true">
                        <DockPanel>
                            <ToggleButton x:Name="HeaderSite" Margin="1" ContentTemplate="{TemplateBinding HeaderTemplate}" Content="{TemplateBinding Header}" ContentTemplateSelector="{TemplateBinding HeaderTemplateSelector}" DockPanel.Dock="Top" FontStretch="{TemplateBinding FontStretch}" Foreground="{TemplateBinding Foreground}" FontStyle="{TemplateBinding FontStyle}" FontFamily="{TemplateBinding FontFamily}" FontWeight="{TemplateBinding FontWeight}" FontSize="{TemplateBinding FontSize}" HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}" IsChecked="{Binding IsExpanded, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}" MinWidth="0" MinHeight="0" Padding="{TemplateBinding Padding}" Style="{StaticResource ExpanderDownHeaderStyle}" VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"/>

                            <ContentPresenter x:Name="ExpandSite" DockPanel.Dock="Bottom" Focusable="false" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}" Visibility="Collapsed"/>
                        </DockPanel>
                    </Border>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsExpanded" Value="true">
                            <Setter Property="Visibility" TargetName="ExpandSite" Value="Visible"/>
                        </Trigger>
                        <Trigger Property="ExpandDirection" Value="Right">
                            <Setter Property="DockPanel.Dock" TargetName="ExpandSite" Value="Right"/>
                            <Setter Property="DockPanel.Dock" TargetName="HeaderSite" Value="Left"/>
                        </Trigger>
                        <Trigger Property="ExpandDirection" Value="Up">
                            <Setter Property="DockPanel.Dock" TargetName="ExpandSite" Value="Top"/>
                            <Setter Property="DockPanel.Dock" TargetName="HeaderSite" Value="Bottom"/>
                        </Trigger>
                        <Trigger Property="ExpandDirection" Value="Left">
                            <Setter Property="DockPanel.Dock" TargetName="ExpandSite" Value="Left"/>
                            <Setter Property="DockPanel.Dock" TargetName="HeaderSite" Value="Right"/>
                        </Trigger>
                        <Trigger Property="IsEnabled" Value="false">

                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

</ResourceDictionary>