如何在wpf中将epander标题鼠标悬停和选定颜色更改为trasparent

我是wpf新手，我不知道如何在鼠标上方将标题颜色更改为透明，并在扩展标题中选择

<DataTemplate >
<StackPanel >


<Expander Name="expander1" Background="Transparent"   Margin="0,0,0,0"   MouseEnter="Expander_MouseEnter"  Width="Auto" Expanded="Expander_Expanded" Collapsed="Expander_Collapsed"    PreviewGotKeyboardFocus="Expander_PreviewGotKeyboardFocus" Style="{DynamicResource PlusMinusExpanderStyle}"  >

<Expander.Header>

<StackPanel  Width="Auto" Height="Auto">

<Grid x:Name="InnerData" Width="Auto"   >
    <Grid.RowDefinitions>
    <RowDefinition  />
    </Grid.RowDefinitions>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="1*"></ColumnDefinition>
        <ColumnDefinition Width="35"></ColumnDefinition>
    </Grid.ColumnDefinitions>


    <TextBlock  Grid.Row="0" Grid.Column="0" Padding="0,18,0,0" Width="Auto"   VerticalAlignment="Center" Text="{Binding Path=sHeader}" Foreground="#FF6E809C" Background="Transparent" FontSize="20" FontWeight="SemiBold" TextTrimming="CharacterEllipsis"  />
    <Image Height="20"  Source="/Images/disclosure_collapsed_copy_30.png" Width="Auto" x:Name="img_collapsed" Grid.Row="0" Grid.Column="1"  Margin="0,18,0,0"></Image>
    <Image Height="20"   Source="/Images/disclosure_expanded_copy_30.png" Width="Auto" x:Name="img_expanded" Visibility="Collapsed" Grid.Row="0" Grid.Column="1" Margin="0,18,0,0"></Image>
</Grid>

您需要使用“VisualStateManager”更改标题的颜色。在要更改颜色的控件内使用以下代码

<VisualStateManager.VisualStateGroups>
    <VisualStateGroup x:Name="CommonStates">
        <VisualState x:Name="Normal" />
        <VisualState x:Name="Pressed"/>
        <VisualState x:Name="MouseOver">
            <Storyboard>
                <ColorAnimationUsingKeyFrames Storyboard.TargetName="HeaderControlName"
                          Storyboard.TargetProperty="(Shape.Fill).(SolidColorBrush.Color)">
                    <EasingColorKeyFrame KeyTime="0"
                   Value="Transparent" />
                </ColorAnimationUsingKeyFrames>
            </Storyboard>
        </VisualState>
    </VisualStateGroup>
</VisualStateManager.VisualStateGroups>

他为什么需要使用“VisualStateManager”？触发器、事件或其他解决方案如何？他是否从VSM中受益？