c# wpf get Name(or Tag) of treeviewitem when clicking on toggleswitch(treearrow) next to item

Question

I have a treeview thats loads 2 subfolder levels. when i click a treeviewitem a method is called that loads 2 subfolder levels from this path. the problem is that i have to call the same method when clicking on the treearrow/toggleswitch next to this item to load the subfolders. so i need the tag of the item when clicking on the treearrow thing to make a directory info object out of it. i have a click event applied to the toggleswitch.

<Style x:Key="ExpandCollapseToggleStyle" TargetType="ToggleButton">
        <Setter Property="Focusable" Value="False"/>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="ToggleButton">
                    <Grid Width="15"
                          Height="13"
                          Background="Transparent">
                        <Path x:Name="ExpandPath"
                              HorizontalAlignment="Left" 
                              VerticalAlignment="Center" 
                              Margin="1,1,1,1"
                              Fill="{StaticResource GlyphBrush}"
                              Data="M 4 0 L 8 4 L 4 8 Z"/>
                    </Grid>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsChecked"
                                 Value="True">
                            <Setter Property="Data"
                                    TargetName="ExpandPath"
                                    Value="M 0 4 L 8 4 L 4 8 Z"/>
                        </Trigger>
                        <Trigger Property="IsPressed" Value="true">

                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
    <Style x:Key="TreeViewItemFocusVisual">
        <Setter Property="Control.Template">
            <Setter.Value>
                <ControlTemplate>
                    <Border>
                        <Rectangle Margin="0,0,0,0"
                                   StrokeThickness="5"
                                   Stroke="Black"
                                   StrokeDashArray="1 2"
                                   Opacity="0"/>
                    </Border>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

    <Style x:Key="{x:Type TreeViewItem}" TargetType="{x:Type TreeViewItem}">
        <Setter Property="Background" Value="Transparent"/>
        <Setter Property="HorizontalContentAlignment" Value="{Binding Path=HorizontalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
        <Setter Property="VerticalContentAlignment" Value="{Binding Path=VerticalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
        <Setter Property="Padding" Value="1,0,0,0"/>
        <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
        <Setter Property="FocusVisualStyle" Value="{StaticResource TreeViewItemFocusVisual}"/>
        <Setter Property="FontSize" Value="15"/>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate 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"
                                      IsChecked="{Binding Path=IsExpanded, RelativeSource={RelativeSource TemplatedParent}}"
                                      ClickMode="Press"
                                      Style="{StaticResource ExpandCollapseToggleStyle}"
                                      Click="onTreeArrowClick"
                                      />
                        <Border Name="Bd"
                                Grid.Column="1"
                                Background="{TemplateBinding Background}"
                                BorderBrush="{TemplateBinding BorderBrush}"
                                BorderThickness="{TemplateBinding BorderThickness}"
                                Padding="{TemplateBinding Padding}">
                            <ContentPresenter x:Name="PART_Header"
                                              ContentSource="Header"
                                              HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"/>
                        </Border>
                        <ItemsPresenter x:Name="ItemsHost"
                                        Grid.Row="1"
                                        Grid.Column="1"
                                        Grid.ColumnSpan="2"/>
                    </Grid>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsExpanded" Value="false">
                            <Setter TargetName="ItemsHost" Property="Visibility" Value="Collapsed"/>
                        </Trigger>
                        <Trigger Property="HasItems" Value="false">
                            <Setter TargetName="Expander" Property="Visibility" Value="Hidden"/>
                        </Trigger>
                        <MultiTrigger>
                            <MultiTrigger.Conditions>
                                <Condition Property="HasHeader" Value="false"/>
                                <Condition Property="Width" Value="Auto"/>
                            </MultiTrigger.Conditions>
                            <Setter TargetName="PART_Header" Property="MinWidth" Value="75"/>
                        </MultiTrigger>
                        <MultiTrigger>
                            <MultiTrigger.Conditions>
                                <Condition Property="HasHeader" Value="false"/>
                                <Condition Property="Height" Value="Auto"/>
                            </MultiTrigger.Conditions>
                            <Setter TargetName="PART_Header" Property="MinHeight" Value="19"/>
                        </MultiTrigger>
                        <Trigger Property="IsSelected" Value="true">
                            <Setter TargetName="Bd" Property="Background" Value="{DynamicResource {x:Static SystemColors.HighlightBrushKey}}"/>
                            <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.HighlightTextBrushKey}}"/>
                        </Trigger>
                        <MultiTrigger>
                            <MultiTrigger.Conditions>
                                <Condition Property="IsSelected" Value="true"/>
                                <Condition Property="IsSelectionActive" Value="false"/>
                            </MultiTrigger.Conditions>
                            <Setter TargetName="Bd" Property="Background" Value="Transparent"/>
                            <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
                        </MultiTrigger>
                        <Trigger Property="IsEnabled" Value="false">
                            <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

Answer 1

Assuming that you gain access to the ToggleButton in your Click event, you need to find its parent of type TreeViewItem . I created an extension method that does this for me... you could edit it to be a normal method if you prefer, or put it into a static class (extension methods need to be in a static class):

public static T GetParentOfType<T>(this DependencyObject element) 
    where T : DependencyObject
{
    Type type = typeof(T);
    if (element == null) return null;
    DependencyObject parent = VisualTreeHelper.GetParent(element);
    if (parent == null && ((FrameworkElement)element).Parent is DependencyObject) 
        parent = ((FrameworkElement)element).Parent;
    if (parent == null) return null;
    else if (parent.GetType() == type || parent.GetType().IsSubclassOf(type)) 
        return parent as T;
    return GetParentOfType<T>(parent);
}

Using this as an extension method, you would call it like this:

TreeViewItem treeViewItem = toggleButton.GetParentOfType<TreeViewItem>();