Implementing WinUI TreeView

When to Use This Skill

• Display hierarchical data in a tree structure (files, folders, categories)
• Implement file explorers or folder browsers in WinUI applications
• Create organization charts or reporting structures
• Build category navigation with expandable/collapsible nodes
• Enable node selection with single or multiple selection modes
• Support inline editing of tree nodes
• Implement drag-and-drop for node reordering or moving
• Load data on demand for large hierarchies
• Customize tree appearance with templates and styling
• Handle CRUD operations on hierarchical data

Component Overview

Key Capabilities

• Dual Data Modes: Bound mode (data binding) and Unbound mode (manual nodes)
• Flexible Selection: Multiple selection modes including Extended with keyboard modifiers
• Inline Editing: Edit node content with custom templates
• Drag-and-Drop: Reorder or move nodes within the tree
• Load on Demand: Lazy load child nodes when parent expands
• Checkboxes: Built-in checkbox support for multi-selection
• Context Menus: Add flyout menus for node operations
• Animations: Smooth expand/collapse animations
• MVVM Support: Full command and data binding support
• Customization: Complete control over appearance with templates

When to Choose TreeView

• Hierarchical visualization of parent-child data
• Expandable/collapsible sections for space-efficient display
• Multiple levels of nesting (2+ levels deep)
• Tree navigation patterns familiar to users

• Flat lists → Use ListView or DataGrid
• Simple grouped data → Use ListView with grouping
• Network/graph relationships → Use custom visualization

Documentation and Navigation Guide

Getting Started

• Installing NuGet package (Syncfusion.TreeView.WinUI)
• Adding TreeView to XAML pages
• Basic TreeView implementation with unbound nodes
• Simple bound mode example with hierarchical data
• Namespace imports and control initialization
• Project configuration

Data Management

• Bound vs Unbound modes comparison
• Hierarchical data source binding with ItemsSource
• ChildPropertyName for self-relational binding
• HierarchyPropertyDescriptors for complex hierarchies
• ItemTemplate and ExpanderTemplate configuration
• ObservableCollection and INotifyPropertyChanged
• NodePopulationMode (OnDemand vs Instant)
• NotificationSubscriptionMode for change tracking

• Enabling drag-and-drop (AllowDragging, AllowDrop)
• Drag-drop events and customization
• Adding nodes programmatically
• Deleting nodes from hierarchy
• Updating node content
• Load on demand implementation
• Context menu operations

User Interaction Features

• SelectionMode options (None, Single, SingleDeselect, Multiple, Extended)
• UI selection with mouse and touch
• Programmatic selection (SelectedItem, SelectedItems)
• Selection events (SelectionChanging, SelectionChanged)
• Keyboard navigation for selection
• Multi-selection with Ctrl/Shift modifiers
• Selection customization and styling

• AutoExpandMode options
• Programmatic expand and collapse
• ExpandAction configuration (single/double tap)
• IsExpanded property usage
• Expand/collapse events
• Expand all and collapse all scenarios
• Maintaining expansion state

• Enabling editing with AllowEditing
• EditTemplate and EditTemplateSelector
• Initiating edit mode (F2 key)
• Committing and canceling edits
• Edit events (ItemBeginEdit, ItemEndEdit)
• Validation during editing
• Bound vs unbound mode editing differences

• Checkbox support and configuration
• Context flyout menus
• Interactive events (ItemTapped, ItemDoubleTapped, ItemHolding)
• Keyboard shortcuts and navigation
• Touch gestures
• Scrolling behavior
• Animation settings (IsAnimationEnabled)

Advanced Features

• MVVM patterns for hierarchical data
• Commands in TreeView
• Data binding best practices
• ViewModel design for tree structures
• Handling ObservableCollections
• Event to command conversions
• Unit testing TreeView ViewModels

Customization

• ItemTemplate for node content
• ExpanderTemplate for expand/collapse icons
• Item height customization (ItemHeight, QueryNodeSize)
• TreeLines configuration
• Indentation and spacing
• Adding icons and images
• Styling selected/hover states
• Theme integration

Quick Start Example

<Page xmlns:treeView="using:Syncfusion.UI.Xaml.TreeView">
    
    <Page.DataContext>
        <local:FileViewModel />
    </Page.DataContext>
    
    <treeView:SfTreeView x:Name="treeView"
                          Width="400"
                          Height="500"
                          ChildPropertyName="SubFiles"
                          ItemsSource="{Binding Files}">
        <treeView:SfTreeView.ItemTemplate>
            <DataTemplate>
                <StackPanel Orientation="Horizontal">
                    <TextBlock Text="📁" Margin="0,0,5,0" />
                    <TextBlock Text="{Binding FileName}" 
                               VerticalAlignment="Center" />
                </StackPanel>
            </DataTemplate>
        </treeView:SfTreeView.ItemTemplate>
    </treeView:SfTreeView>
    
</Page>

public class FileViewModel : INotifyPropertyChanged
{
    public ObservableCollection<FileNode> Files { get; set; }
    
    public FileViewModel()
    {
        Files = new ObservableCollection<FileNode>
        {
            new FileNode 
            { 
                FileName = "Documents",
                SubFiles = new ObservableCollection<FileNode>
                {
                    new FileNode { FileName = "Resume.docx" },
                    new FileNode { FileName = "CoverLetter.pdf" }
                }
            },
            new FileNode 
            { 
                FileName = "Downloads",
                SubFiles = new ObservableCollection<FileNode>()
            }
        };
    }
    
    public event PropertyChangedEventHandler PropertyChanged;
}

public class FileNode : INotifyPropertyChanged
{
    private string _fileName;
    private ObservableCollection<FileNode> _subFiles;
    
    public string FileName
    {
        get => _fileName;
        set { _fileName = value; OnPropertyChanged(); }
    }
    
    public ObservableCollection<FileNode> SubFiles
    {
        get => _subFiles;
        set { _subFiles = value; OnPropertyChanged(); }
    }
    
    public event PropertyChangedEventHandler PropertyChanged;
    
    protected void OnPropertyChanged([CallerMemberName] string name = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
    }
}

Common Patterns

Pattern 1: File Explorer with Icons

<treeView:SfTreeView ItemsSource="{Binding Items}"
                      ChildPropertyName="Children">
    <treeView:SfTreeView.ItemTemplate>
        <DataTemplate>
            <StackPanel Orientation="Horizontal">
                <FontIcon Glyph="{Binding Icon}" 
                          FontSize="16" 
                          Margin="0,0,8,0" />
                <TextBlock Text="{Binding Name}" />
            </StackPanel>
        </DataTemplate>
    </treeView:SfTreeView.ItemTemplate>
</treeView:SfTreeView>

Pattern 2: Multiple Selection with Checkboxes

<treeView:SfTreeView SelectionMode="Multiple"
                      CheckBoxMode="Recursive">
    <!-- When parent checked, all children auto-check -->
</treeView:SfTreeView>

Pattern 3: Load on Demand

<treeView:SfTreeView LoadOnDemand="True"
                      LoadOnDemandCommand="{Binding LoadChildrenCommand}">
    <!-- Children load only when node expands -->
</treeView:SfTreeView>

Pattern 4: Programmatic Selection

// Single selection
treeView.SelectedItem = viewModel.RootNode.Children[0];

// Multiple selection
treeView.SelectedItems.Add(node1);
treeView.SelectedItems.Add(node2);

// Select all nodes
treeView.SelectAll();

Pattern 5: Context Menu Operations

<treeView:SfTreeView ItemHolding="OnItemHolding">
    <!-- Show context menu on right-click/long-press -->
</treeView:SfTreeView>

private void OnItemHolding(object sender, ItemHoldingEventArgs e)
{
    var flyout = new MenuFlyout();
    flyout.Items.Add(new MenuFlyoutItem { Text = "Rename" });
    flyout.Items.Add(new MenuFlyoutItem { Text = "Delete" });
    flyout.ShowAt(e.Element);
}

Key Properties and Methods

Essential Properties

Key Methods

Important Events

Common Use Cases

Use Case 1: File System Browser

• Bound mode with hierarchical data
• Custom ItemTemplate with icons
• Context flyout menus
• Drag-and-drop for moving files

Use Case 2: Organization Chart

• Bound mode with employee data
• AutoExpandMode for initial display
• Single selection mode
• Custom templates for employee cards

Use Case 3: Product Category Browser

• Load on demand for large catalogs
• Single selection
• Custom styling for categories
• Click events for navigation

Use Case 4: Settings Panel

• Unbound mode with manual nodes
• AutoExpandMode for convenience
• Custom ItemTemplate for settings controls
• Maintain expansion state

Use Case 5: Project Explorer (IDE-like)

• Bound mode with solution model
• Inline editing for renaming
• Drag-drop for reorganizing
• Context menus for file operations
• Multiple selection for batch operations

Performance Tips

• Use OnDemand NodePopulationMode for large hierarchies (1000+ nodes)
• Set NotificationSubscriptionMode to CollectionChanged only if needed
• Use x:Bind instead of Binding for better performance
• Minimize complexity in ItemTemplate
• Use LoadOnDemand for deep hierarchies with many children
• Consider virtualization for very large flat sections

Troubleshooting Quick Reference

Related Components

• ListView - For flat lists without hierarchy
• DataGrid - For tabular data with hierarchy support (TreeGrid)
• Expander - For simple expand/collapse sections

getting-started.md