Hier ist mein Code -

<Style x:Key="CustomComboBox" TargetType="{x:Type ComboBox}">
    <Setter Property="SnapsToDevicePixels" Value="true"/>
    <Setter Property="FontSize" Value="18"/>
    <Setter Property="Background" Value="LightGray"/>
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type ComboBox}">
                <Grid>
                    <Grid.Resources>
// This part, I want to set dynamically
                        <SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}" Color="{TemplateBinding BorderBrush}"></SolidColorBrush>
                    </Grid.Resources>
                    <ToggleButton Grid.Column="2" Template="{StaticResource ComboBoxToggleButton}" x:Name="ToggleButton" Focusable="false" IsChecked="{Binding Path=IsDropDownOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}" ClickMode="Press" Background="{TemplateBinding Background}" Foreground="{TemplateBinding Foreground}" BorderBrush="{TemplateBinding BorderBrush}"/>
                    <ContentPresenter HorizontalAlignment="Left" Margin="10,3,23,3" x:Name="Content" VerticalAlignment="Center" Content="{TemplateBinding SelectionBoxItem}" ContentTemplate="{TemplateBinding SelectionBoxItemTemplate}" ContentTemplateSelector="{TemplateBinding ItemTemplateSelector}" IsHitTestVisible="False"/>
                    <TextBox x:Name="PART_EditableTextBox" Visibility="Hidden" Template="{StaticResource ComboBoxTextBox}" HorizontalAlignment="Left" Margin="3,3,23,3" Style="{x:Null}" VerticalAlignment="Center" Focusable="True" Background="{TemplateBinding Background}" Foreground="{TemplateBinding Foreground}" IsReadOnly="{TemplateBinding IsReadOnly}" FontSize="{TemplateBinding FontSize}"/>
                                            <Popup Placement="Center" x:Name="Popup" Focusable="False" AllowsTransparency="True" 
                           IsOpen="{TemplateBinding IsDropDownOpen}"  PopupAnimation="Fade" VerticalOffset="-2">

                        <Grid MinWidth="{TemplateBinding ActualWidth}" MaxHeight="{TemplateBinding MaxDropDownHeight}"
                              x:Name="DropDown" SnapsToDevicePixels="True">
                            <Border BorderBrush="LightGray" BorderThickness="1,1,1,1" x:Name="DropDownBorder" Background="White"  />
                            <ScrollViewer x:Name="ScrollViewer" Template="{DynamicResource CustomScrollViewerControlTemplate}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="0" Margin="4,6,4,6" SnapsToDevicePixels="True" HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto" CanContentScroll="True">
                               <ItemsPresenter KeyboardNavigation.DirectionalNavigation="Contained" />
                            </ScrollViewer>
                        </Grid>
                    </Popup>
                </Grid>
                <ControlTemplate.Triggers>
                        <Trigger Property="HasItems" Value="false">
                        <Setter Property="MinHeight" Value="95" TargetName="DropDownBorder"/>
                    </Trigger>
                    <Trigger Property="IsEnabled" Value="false">
                        <Setter Property="Foreground" Value="LightGray"/>
                    </Trigger>
                    <Trigger Property="IsGrouping" Value="true">
                        <Setter Property="ScrollViewer.CanContentScroll" Value="false"/>
                    </Trigger>
                    <Trigger Property="AllowsTransparency" SourceName="Popup" Value="true">
                        <Setter Property="Margin" Value="0,2,0,0" TargetName="DropDownBorder"/>
                    </Trigger>
                    <Trigger Property="IsEditable" Value="true">
                        <Setter Property="IsTabStop" Value="false"/>
                        <Setter Property="Visibility" Value="Visible" TargetName="PART_EditableTextBox"/>
                        <Setter Property="Visibility" Value="Hidden" TargetName="ContentSite"/>
                    </Trigger>
                </ControlTemplate.Triggers>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

Ich erstelle Custom ComboBox. Hier versuche ich, den BorderBrush-Wert aus dem TemplateBinding von ComboBox zu erhalten. Aber ich verstehe es nicht. Es ist immer weiß. Ich weiß nicht, warum es passiert, vielleicht ist meine Art, den Pinsel zu bekommen, falsch.

Bitte vorschlagen.