Tenho uma exibição em árvore do wpf que exibe nós de vários tipos com imagens correspondentes, como imagens de pastas. Inicialmente, a árvore e seus nós com imagens correspondentes são exibidos conforme o esperado. No entanto, quando um nó é expandido, a expectativa é que a imagem para o nó expandido seja trocada por uma imagem expandida. Estou tentando usarHierarchicalDataTemplate dispara para configurar isso.

s acionadores devem ser configurados de maneira diferent

A árvore se parece com:

(Folder Image) Solutions (SolutionsViewModel)
--(Solution Image) Solution 1 (Solution)
--(Solution Image) Solution 2 (Solution)
(Folder Image) Conventions (ConventionsViewModel)

O xaml dos nós principais na visualização em árvore (o tema está vazio):

<UserControl.Resources>
    <ResourceDictionary>
        <ResourceDictionary.MergedDictionaries>
            <ResourceDictionary Source="../Theme.xaml" />
        </ResourceDictionary.MergedDictionaries>

        <HierarchicalDataTemplate DataType="{x:Type vm:SolutionsViewModel}" ItemsSource="{Binding Items}">
            <StackPanel Orientation="Horizontal">
                <Image x:Name="nodeImg" Width="16" Height="16" Source="pack://siteOfOrigin:,,,/Resources/FolderClosed.bmp"/>
                <TextBlock Margin="5,0,0,0" Text="{Binding Name}" />
            </StackPanel>
            <HierarchicalDataTemplate.Triggers>
                <DataTrigger Binding="{Binding IsExpanded}" Value="True">
                    <Setter TargetName="nodeImg" Property="Source" Value="pack://siteOfOrigin:,,,/Resources//FolderOpen.bmp"/>
                </DataTrigger>
            </HierarchicalDataTemplate.Triggers>
        </HierarchicalDataTemplate>

        <HierarchicalDataTemplate DataType="{x:Type sol:Solution}" ItemsSource="{Binding Items}">
            <StackPanel Orientation="Horizontal">
                <Image x:Name="treeImg" Width="16" Height="16" Source="pack://siteOfOrigin:,,,/Resources/SolutionClosed.bmp"/>
                <TextBlock Margin="5,0,0,0" Text="{Binding Name}" />
            </StackPanel>
            <HierarchicalDataTemplate.Triggers>
                <DataTrigger Binding="{Binding IsExpanded}" Value="True">
                    <Setter TargetName="treeImg" Property="Source" Value="pack://siteOfOrigin:,,,/Resources//SolutionOpen.bmp"/>
                </DataTrigger>
            </HierarchicalDataTemplate.Triggers>
        </HierarchicalDataTemplate>

        <HierarchicalDataTemplate DataType="{x:Type vm:ConventionsViewModel}" ItemsSource="{Binding Items}">
            <StackPanel Orientation="Horizontal">
                <Image x:Name="nodeImg" Width="16" Height="16" Source="pack://siteOfOrigin:,,,/Resources/FolderClosed.bmp"/>
                <TextBlock Margin="5,0,0,0" Text="{Binding Name}" />
            </StackPanel>
            <HierarchicalDataTemplate.Triggers>
                <DataTrigger Binding="{Binding IsExpanded}" Value="True">
                    <Setter TargetName="nodeImg" Property="Source" Value="pack://siteOfOrigin:,,,/Resources//FolderOpen.bmp"/>
                </DataTrigger>
            </HierarchicalDataTemplate.Triggers>
        </HierarchicalDataTemplate>
    </ResourceDictionary>
</UserControl.Resources>
<UserControl.DataContext>
    <ObjectDataProvider 
    ObjectType="{x:Type vm:TreeViewModel}"
    MethodName="CreateDefaultTree"
    />
</UserControl.DataContext>
<ScrollViewer VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Auto">
    <Grid>
        <TreeView Name="solutionsModel" ItemsSource="{Binding Items}">
            <TreeView.ItemContainerStyle>
                <Style TargetType="{x:Type TreeViewItem}">
                    <Setter Property="IsExpanded" Value="{Binding IsExpanded, Mode=TwoWay}" />
                    <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}" />
                    <Setter Property="FontWeight" Value="Normal" />
                    <Style.Triggers>
                        <Trigger Property="IsSelected" Value="True">
                            <Setter Property="FontWeight" Value="Bold" />
                        </Trigger>
                    </Style.Triggers>
                </Style>
            </TreeView.ItemContainerStyle>
        </TreeView>
    </Grid>
</ScrollViewer>