ShrlAlgoToolkit/WPFDark/StandardControls/TreeView.xaml

<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:controls="clr-namespace:WPFDark.Controls"
    xmlns:internals="clr-namespace:WPFDark.Internals"
    xmlns:wpf="clr-namespace:WPFDark"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <Style TargetType="{x:Type TreeView}">
        <Setter Property="Background" Value="{DynamicResource TextBoxBackgroundBrushKey}" />
        <Setter Property="BorderBrush" Value="{DynamicResource TextBoxBorderBrushKey}" />
        <Setter Property="BorderThickness" Value="1" />
        <Setter Property="Foreground" Value="{DynamicResource TextBoxForegroundBrushKey}" />
        <Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Auto" />
        <Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Auto" />
        <Setter Property="ScrollViewer.CanContentScroll" Value="True" />
        <Setter Property="ScrollViewer.PanningMode" Value="Both" />
        <Setter Property="Stylus.IsFlicksEnabled" Value="False" />
        <Setter Property="VerticalContentAlignment" Value="Center" />

        <Setter Property="VirtualizingPanel.IsVirtualizing" Value="True" />
        <Setter Property="VirtualizingPanel.VirtualizationMode" Value="Recycling" />
        <Setter Property="VirtualizingStackPanel.ScrollUnit" Value="Pixel" />
        <Setter Property="VirtualizingStackPanel.CacheLength" Value="20,20" />
        <Setter Property="VirtualizingStackPanel.CacheLengthUnit" Value="Item" />

        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="TreeView">
                    <controls:BiaClippingBorder
                        Background="{TemplateBinding Background}"
                        BorderBrush="{TemplateBinding BorderBrush}"
                        BorderThickness="{TemplateBinding BorderThickness}"
                        CornerRadius="{x:Static wpf:Boxes.GroupCornerRadius}"
                        x:Name="Bd">
                        <ScrollViewer Focusable="False">
                            <ItemsPresenter />
                        </ScrollViewer>
                    </controls:BiaClippingBorder>
                </ControlTemplate>
            </Setter.Value>
        </Setter>

        <Style.Triggers>
            <Trigger Property="IsEnabled" Value="False">
                <Setter Property="Background" Value="{DynamicResource InactiveBackgroundBrushKey}" />
                <Setter Property="BorderBrush" Value="{DynamicResource InactiveBorderBrushKey}" />
                <Setter Property="Foreground" Value="{DynamicResource InactiveForegroundBrushKey}" />
            </Trigger>
        </Style.Triggers>
    </Style>

    <!--  https://stackoverflow.com/questions/664632/highlight-whole-treeviewitem-line-in-wpf  -->

    <Style TargetType="ToggleButton" x:Key="ExpandCollapseToggleStyle">
        <Setter Property="Focusable" Value="False" />
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="ToggleButton">
                    <Canvas
                        Background="Transparent"
                        Height="15"
                        Width="15">
                        <Path Data="M 5.367188 10.363281 L 8.230469 7.5 L 5.367188 4.632812 L 6.25 3.75 L 10 7.5 L 6.25 11.25 Z M 5.367188 10.363281" x:Name="ExpandPath">
                            <Path.Style>
                                <Style TargetType="{x:Type Path}">
                                    <Setter Property="Fill" Value="{DynamicResource ForegroundBrushKey}" />
                                    <Style.Triggers>
                                        <Trigger Property="IsEnabled" Value="False">
                                            <Setter Property="Fill" Value="{DynamicResource InactiveForegroundBrushKey}" />
                                        </Trigger>
                                    </Style.Triggers>
                                </Style>
                            </Path.Style>
                        </Path>
                    </Canvas>

                    <ControlTemplate.Triggers>
                        <Trigger Property="IsChecked" Value="True">
                            <Setter Property="Data" TargetName="ExpandPath" Value="M 4.632812 5.363281 L 7.5 8.230469 L 10.367188 5.363281 L 11.25 6.25 L 7.5 10 L 3.75 6.25 Z M 4.632812 5.363281" />
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

    <Style x:Key="TreeViewItemFocusVisualStyle">
        <Setter Property="Control.Template">
            <Setter.Value>
                <ControlTemplate>
                    <Border>
                        <Rectangle
                            Margin="0"
                            Opacity="0.0"
                            Stroke="White"
                            StrokeDashArray="1 2"
                            StrokeThickness="5.0" />
                    </Border>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

    <Style TargetType="{x:Type TreeViewItem}" x:Key="{x:Type TreeViewItem}">
        <Setter Property="Background" Value="Transparent" />
        <Setter Property="BorderBrush" Value="Transparent" />
        <Setter Property="Padding" Value="1" />
        <Setter Property="BorderThickness" Value="0" />
        <Setter Property="HorizontalContentAlignment" Value="{Binding HorizontalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}" />
        <Setter Property="VerticalContentAlignment" Value="{Binding VerticalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}" />
        <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}" />
        <Setter Property="FocusVisualStyle" Value="{StaticResource TreeViewItemFocusVisualStyle}" />

        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type TreeViewItem}">
                    <StackPanel>
                        <Border
                            Background="{TemplateBinding Background}"
                            BorderBrush="{TemplateBinding BorderBrush}"
                            BorderThickness="{TemplateBinding BorderThickness}"
                            Name="Bd"
                            Padding="{TemplateBinding Padding}">
                            <Grid>
                                <Grid.Style>
                                    <Style TargetType="{x:Type Grid}">
                                        <Setter Property="Margin">
                                            <Setter.Value>
                                                <MultiBinding Converter="{x:Static wpf:Constants.LengthConverter}">
                                                    <Binding RelativeSource="{RelativeSource TemplatedParent}" />
                                                </MultiBinding>
                                            </Setter.Value>
                                        </Setter>
                                    </Style>
                                </Grid.Style>

                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="19" />
                                    <ColumnDefinition />
                                </Grid.ColumnDefinitions>

                                <!--  x:NameはWPFDark.Internals.Constants.TreeViewItemExpanderName  -->
                                <ToggleButton
                                    ClickMode="Press"
                                    IsChecked="{Binding IsExpanded, RelativeSource={RelativeSource TemplatedParent}}"
                                    Style="{StaticResource ExpandCollapseToggleStyle}"
                                    x:Name="Expander" />

                                <ContentPresenter
                                    ContentSource="Header"
                                    Grid.Column="1"
                                    HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
                                    x:Name="PART_Header" />
                            </Grid>
                        </Border>
                        <ItemsPresenter x:Name="ItemsHost" />
                    </StackPanel>

                    <ControlTemplate.Triggers>
                        <Trigger Property="internals:TreeViewHelper.IsMouseDirectlyOverItem" Value="True">
                            <Setter Property="Background" TargetName="Bd" Value="{DynamicResource ActiveBackgroundBrushKey}" />
                            <Setter Property="BorderBrush" TargetName="Bd" Value="{DynamicResource ActiveBackgroundBrushKey}" />
                        </Trigger>

                        <Trigger Property="IsExpanded" Value="False">
                            <Setter Property="Visibility" TargetName="ItemsHost" Value="Collapsed" />
                        </Trigger>
                        <Trigger Property="HasItems" Value="False">
                            <Setter Property="Visibility" TargetName="Expander" Value="Hidden" />
                        </Trigger>

                        <Trigger Property="IsSelected" Value="True">
                            <Setter Property="Background" TargetName="Bd" Value="{DynamicResource Item.SelectedInactive.Background}" />
                            <Setter Property="BorderBrush" TargetName="Bd" Value="{DynamicResource Item.SelectedInactive.Border}" />
                        </Trigger>

                        <MultiTrigger>
                            <MultiTrigger.Conditions>
                                <Condition Property="IsSelected" Value="True" />
                                <Condition Property="IsMouseOver" Value="True" />
                            </MultiTrigger.Conditions>
                            <Setter Property="Background" TargetName="Bd" Value="{DynamicResource Item.SelectedActive.Background.IsMouseOver}" />
                            <Setter Property="BorderBrush" TargetName="Bd" Value="{DynamicResource Item.SelectedActive.Border.IsMouseOver}" />
                        </MultiTrigger>

                        <Trigger Property="IsEnabled" Value="False">
                            <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}" />
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</ResourceDictionary>