This example illustrates how to change the icon of a node when expanding in WPF TreeView (SfTreeView)?
WPF TreeView (SfTreeView) does not provide the direct support to change the icon of a node while expanding. You can change the icon of a node while expanding by using ItemTemplateSelector in WPF TreeView (SfTreeView). The WPF TreeView (SfTreeView) allows you to customize the appearance of each item with different templates based on specific constraints by using the ItemTemplateSelector. You can choose a DataTemplate for each item at runtime based on the value of data-bound property using ItemTemplateSelector.
<Window.Resources>
<DataTemplate x:Key="descriptionTemplate">
<Grid x:Name="grid">
<Grid Grid.Row="0">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="20" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<Grid>
<Image Source="{Binding Content.ImageIcon}"
VerticalAlignment="Center"
HorizontalAlignment="Center"
Height="16"
Width="16"/>
</Grid>
<Grid Grid.Column="1"
Margin="1,0,0,0"
VerticalAlignment="Center">
<Label Content="{Binding Content.ItemName}"
Foreground="Black"
FontSize="12"
VerticalContentAlignment="Center" />
</Grid>
</Grid>
</Grid>
</DataTemplate>
<DataTemplate x:Key="headerTemplate">
<Grid x:Name="grid">
<Grid Grid.Row="0">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="20" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<Grid>
<!--by defalut show the icon for content-->
<Image Source="{Binding Content.ImageIcon}"
VerticalAlignment="Center"
HorizontalAlignment="Center"
Height="16"
Width="16"/>
</Grid>
<Grid Grid.Column="1"
Margin="1,0,0,0"
VerticalAlignment="Center">
<Label Content="{Binding Content.ItemName}"
Foreground="Teal"
FontSize="12"
VerticalContentAlignment="Center" />
</Grid>
</Grid>
</Grid>
</DataTemplate>
<DataTemplate x:Key="headerTemplate1">
<Grid x:Name="grid">
<Grid Grid.Row="0">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="20" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<Grid>
<!--While expanding node. In this case added the Icon for CloseFolder in template-->
<Image Source="pack://application:,,,/SfTreeViewDemo;component/Icons/treeview_folderClose.png"
VerticalAlignment="Center"
HorizontalAlignment="Center"
Height="16"
Width="16"/>
</Grid>
<Grid Grid.Column="1"
Margin="1,0,0,0"
VerticalAlignment="Center">
<Label Content="{Binding Content.ItemName}"
Foreground="Teal"
FontSize="12"
VerticalContentAlignment="Center" />
</Grid>
</Grid>
</Grid>
</DataTemplate>
<local:ItemTemplateSelector x:Key="itemTemplateSelector"/>
</Window.Resources>
<Grid>
<syncfusion:SfTreeView x:Name="sfTreeView"
Grid.Row="1"
AutoExpandMode="RootNodes"
ChildPropertyName="SubFiles"
ItemsSource="{Binding ImageNodeInfo}"
ItemTemplateSelector="{StaticResource itemTemplateSelector}"
ItemTemplateDataContextType="Node" >
</syncfusion:SfTreeView>
</Grid>
class ItemTemplateSelector : DataTemplateSelector
{
public override DataTemplate SelectTemplate(object item, DependencyObject container)
{
var treeviewNode = item as TreeViewNode;
if (treeviewNode == null)
return null;
//Check the conditionn for Node expande or Collapsed
if (treeviewNode.IsExpanded)
{
DataTemplate dataTemplate = ((FrameworkElement)container).FindResource("headerTemplate") as DataTemplate;
//while Node expanded state added the FolderOpen Icon in below mentioed temaplate
return dataTemplate;
}
else
{
DataTemplate dataTemplate = ((FrameworkElement)container).FindResource("headerTemplate1") as DataTemplate;
//while node collapsed state added the FolderClose Icon in below mentioed temaplate
return dataTemplate;
}
}
}
The following screenshot shows to change the icon of a node while expanding in WPF TreeView (SfTreeView),
Take a moment to peruse the WPF TreeView - Appearance documentation, where you can find about appearance with code examples.
KB article - How to change the icon of a node when expanding in WPF TreeView (SfTreeView)?
Visual Studio 2015 and above versions