Question

I am searching for a WPF TreeView equivalent of TreeView.HideSelection = false. Does someone have an idea?

Answer 1

If my understanding of TreeView.HideSelection is correct, place the following in your resources:

<ControlTemplate x:Key="StaysHighlightedTreeViewItemTemplate" TargetType="{x:Type TreeViewItem}">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition MinWidth="19" Width="Auto"/>
            <ColumnDefinition Width="Auto"/>
            <ColumnDefinition Width="*"/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition/>
        </Grid.RowDefinitions>
        <ToggleButton x:Name="Expander" ClickMode="Press" IsChecked="{Binding IsExpanded, RelativeSource={RelativeSource TemplatedParent}}">
            <ToggleButton.Style>
                <Style TargetType="{x:Type ToggleButton}">
                    <Setter Property="Focusable" Value="False"/>
                    <Setter Property="Width" Value="16"/>
                    <Setter Property="Height" Value="16"/>
                    <Setter Property="Template">
                        <Setter.Value>
                            <ControlTemplate TargetType="{x:Type ToggleButton}">
                                <Border Background="Transparent" Height="16" Padding="5" Width="16">
                                    <Path x:Name="ExpandPath" Data="M0,0 L0,6 L6,0 z" Fill="Transparent" Stroke="#FF989898">
                                        <Path.RenderTransform>
                                            <RotateTransform Angle="135" CenterY="3" CenterX="3"/>
                                        </Path.RenderTransform>
                                    </Path>
                                </Border>
                                <ControlTemplate.Triggers>
                                    <Trigger Property="IsMouseOver" Value="True">
                                        <Setter Property="Stroke" TargetName="ExpandPath" Value="#FF1BBBFA"/>
                                        <Setter Property="Fill" TargetName="ExpandPath" Value="Transparent"/>
                                    </Trigger>
                                    <Trigger Property="IsChecked" Value="True">
                                        <Setter Property="RenderTransform" TargetName="ExpandPath">
                                            <Setter.Value>
                                                <RotateTransform Angle="180" CenterY="3" CenterX="3"/>
                                            </Setter.Value>
                                        </Setter>
                                        <Setter Property="Fill" TargetName="ExpandPath" Value="#FF595959"/>
                                        <Setter Property="Stroke" TargetName="ExpandPath" Value="#FF262626"/>
                                    </Trigger>
                                </ControlTemplate.Triggers>
                            </ControlTemplate>
                        </Setter.Value>
                    </Setter>
                </Style>
            </ToggleButton.Style>
        </ToggleButton>
        <Border x:Name="Bd" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Grid.Column="1" Padding="{TemplateBinding Padding}" SnapsToDevicePixels="True">
            <ContentPresenter x:Name="PART_Header" ContentTemplate="{TemplateBinding HeaderTemplate}" Content="{TemplateBinding Header}" ContentStringFormat="{TemplateBinding HeaderStringFormat}" ContentSource="Header" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
        </Border>
        <ItemsPresenter x:Name="ItemsHost" Grid.ColumnSpan="2" Grid.Column="1" Grid.Row="1"/>
    </Grid>
    <ControlTemplate.Triggers>
        <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 {x:Static SystemColors.HighlightBrushKey}}"/>
            <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.HighlightTextBrushKey}}"/>
        </Trigger>
        <Trigger Property="IsEnabled" Value="False">
            <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
        </Trigger>
    </ControlTemplate.Triggers>
</ControlTemplate>

<Style x:Key="StaysHighlightedTreeViewItem" TargetType="{x:Type TreeViewItem}">
    <Setter Property="Template" Value="{StaticResource StaysHighlightedTreeViewItemTemplate}"/>
</Style>

Then use the style like so:

<TreeView ItemContainerStyle="{StaticResource StaysHighlightedTreeViewItem}" />

The default control template has the following trigger:

<MultiTrigger>
    <MultiTrigger.Conditions>
        <Condition Property="IsSelected" Value="True"/>
        <Condition Property="IsSelectionActive" Value="False"/>
    </MultiTrigger.Conditions>
    <Setter Property="Background" TargetName="Bd" Value="{DynamicResource {x:Static SystemColors.ControlBrushKey}}"/>
    <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
</MultiTrigger>

This changed the highlighting of the selected item when the selection was not active (i.e. did not have keyboard focus), by removing this trigger the standard highlighting is used even when it does not have focus.