有人可以帮我弄清楚我的模板有什么问题吗？我修改了默认模板，因为我希望根据每个节点的Tag属性值显示树节点的不同图标。它仅显示根节点及其直接第一个子节点的图标。所有其余节点都显示没有图标：
<Style TargetType="TreeViewItem" BasedOn="{StaticResource {x:Type TreeViewItem}}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="TreeViewItem">
<StackPanel>
<Grid Margin="0">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto" MinWidth="16" />
<ColumnDefinition Width="Auto" MinWidth="20" />
<ColumnDefinition Width="*" />
<ColumnDefinition Width="Auto" MinWidth="20" />
<ColumnDefinition Width="Auto" MinWidth="20" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition />
</Grid.RowDefinitions>
<ToggleButton IsChecked="{Binding Path=IsExpanded, RelativeSource={RelativeSource TemplatedParent}}" ClickMode="Press" Name="Expander">
<ToggleButton.Style>
<Style TargetType="ToggleButton">
<Setter Property="UIElement.Focusable" Value="false" />
<Setter Property="FrameworkElement.Width" Value="16" />
<Setter Property="FrameworkElement.Height" Value="16" />
<Setter Property="Control.Template">
<Setter.Value>
<ControlTemplate TargetType="ToggleButton">
<Border Padding="5,5,5,5" Background="#00FFFFFF" Width="16" Height="16">
<Path Fill="#00FFFFFF" Stroke="#FF989898" Name="ExpandPath">
<Path.Data>
<PathGeometry Figures="M0,0L0,6L6,0z" />
</Path.Data>
<Path.RenderTransform>
<RotateTransform Angle="135" CenterX="3" CenterY="3" />
</Path.RenderTransform>
</Path>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="UIElement.IsMouseOver" Value="True">
<Setter TargetName="ExpandPath" Property="Shape.Stroke" Value="#FF1BBBFA" />
<Setter TargetName="ExpandPath" Property="Shape.Fill" Value="#00FFFFFF" />
</Trigger>
<Trigger Property="ToggleButton.IsChecked" Value="True">
<Setter TargetName="ExpandPath" Property="UIElement.RenderTransform">
<Setter.Value>
<RotateTransform Angle="180" CenterX="3" CenterY="3" />
</Setter.Value>
</Setter>
<Setter TargetName="ExpandPath" Property="Shape.Fill" Value="#FF595959" />
<Setter TargetName="ExpandPath" Property="Shape.Stroke" Value="#FF262626" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</ToggleButton.Style>
</ToggleButton>
<ContentPresenter Grid.Column="1">
<ContentPresenter.Style>
<Style TargetType="{x:Type ContentPresenter}">
<Style.Triggers>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource AncestorType={x:Type TreeViewItem}}, Path=Tag}" Value="2">
<Setter Property="Content">
<Setter.Value>
<Ellipse Width="6" Height="6" Fill="Black" Stroke="Black" />
</Setter.Value>
</Setter>
</DataTrigger>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource AncestorType={x:Type TreeViewItem}}, Path=Tag}" Value="1">
<Setter Property="Content">
<Setter.Value>
<Image Width="16" Height="16" Stretch="Uniform" Grid.Column="1" Source="..\Resources\1432599157_layers.png" />
</Setter.Value>
</Setter>
</DataTrigger>
</Style.Triggers>
</Style>
</ContentPresenter.Style>
</ContentPresenter>
<Border x:Name="Bd" HorizontalAlignment="Stretch" BorderThickness="{TemplateBinding Border.BorderThickness}" BorderBrush="{TemplateBinding Border.BorderBrush}"
Padding="{TemplateBinding Control.Padding}" SnapsToDevicePixels="True" Grid.Column="2" Grid.ColumnSpan="3">
<ContentPresenter x:Name="PART_Header"
Content="{TemplateBinding HeaderedContentControl.Header}"
ContentTemplate="{TemplateBinding HeaderedContentControl.HeaderTemplate}"
ContentStringFormat="{TemplateBinding HeaderedItemsControl.HeaderStringFormat}"
ContentTemplateSelector="{TemplateBinding HeaderedItemsControl.HeaderTemplateSelector}"
ContentSource="Header"
HorizontalAlignment="Left"
SnapsToDevicePixels="{TemplateBinding UIElement.SnapsToDevicePixels}" />
</Border>
<ItemsPresenter HorizontalAlignment="Stretch" x:Name="ItemsHost" Grid.Row="1" Grid.Column="2" Grid.ColumnSpan="3" />
</Grid>
</StackPanel>
<ControlTemplate.Triggers>
<Trigger Property="TreeViewItem.IsExpanded" Value="False">
<Setter TargetName="ItemsHost" Property="UIElement.Visibility" Value="Collapsed" />
</Trigger>
<Trigger Property="ItemsControl.HasItems" Value="False">
<Setter TargetName="Expander" Property="UIElement.Visibility" Value="Hidden" />
</Trigger>
<Trigger Property="TreeViewItem.IsSelected" Value="True">
<Setter TargetName="Bd" Property="Panel.Background" Value="{DynamicResource {x:Static SystemColors.HighlightBrushKey}}" />
<Setter Property="TextElement.Foreground" Value="{DynamicResource {x:Static SystemColors.HighlightTextBrushKey}}" />
</Trigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="TreeViewItem.IsSelected" Value="True" />
<Condition Property="Selector.IsSelectionActive" Value="False" />
</MultiTrigger.Conditions>
<Setter TargetName="Bd" Property="Panel.Background" Value="{DynamicResource {x:Static SystemColors.ControlBrushKey}}" />
<Setter Property="TextElement.Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}" />
</MultiTrigger>
<Trigger Property="UIElement.IsEnabled" Value="False">
<Setter Property="TextElement.Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>