<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:syncfusion="http://schemas.syncfusion.com/wpf"
        xmlns:Engine="clr-namespace:Syncfusion.UI.Xaml.TreeView.Engine;assembly=Syncfusion.SfTreeView.WPF">
    <Grid>
        <syncfusion:SfTreeView x:Name="treeView" Width="300">
            <syncfusion:SfTreeView.Nodes>
                <Engine:TreeViewNode Content="Documents" IsExpanded="True">
                    <Engine:TreeViewNode.ChildNodes>
                        <Engine:TreeViewNode Content="Reports"/>
                        <Engine:TreeViewNode Content="Invoices"/>
                    </Engine:TreeViewNode.ChildNodes>
                </Engine:TreeViewNode>
                <Engine:TreeViewNode Content="Pictures" IsExpanded="True">
                    <Engine:TreeViewNode.ChildNodes>
                        <Engine:TreeViewNode Content="Vacation"/>
                        <Engine:TreeViewNode Content="Family"/>
                    </Engine:TreeViewNode.ChildNodes>
                </Engine:TreeViewNode>
            </syncfusion:SfTreeView.Nodes>
        </syncfusion:SfTreeView>
    </Grid>
</Window>

<syncfusion:SfTreeView x:Name="treeView"
                       ItemsSource="{Binding Folders}"
                       ChildPropertyName="SubFolders"
                       AutoExpandMode="RootNodes">
    <syncfusion:SfTreeView.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding FolderName}" 
                       VerticalAlignment="Center"/>
        </DataTemplate>
    </syncfusion:SfTreeView.ItemTemplate>
</syncfusion:SfTreeView>

// ViewModel
public class ViewModel : INotifyPropertyChanged
{
    public ObservableCollection<Folder> Folders { get; set; }
    
    public ViewModel()
    {
        Folders = new ObservableCollection<Folder>
        {
            new Folder 
            { 
                FolderName = "Documents",
                SubFolders = new ObservableCollection<Folder>
                {
                    new Folder { FolderName = "Reports" },
                    new Folder { FolderName = "Invoices" }
                }
            }
        };
    }
}

public class Folder : INotifyPropertyChanged
{
    public string FolderName { get; set; }
    public ObservableCollection<Folder> SubFolders { get; set; }
}

<syncfusion:SfTreeView x:Name="treeView"
                       ItemsSource="{Binding Items}"
                       ChildPropertyName="Children"
                       SelectionMode="Multiple"
                       CheckBoxMode="Recursive"
                       CheckedItems="{Binding CheckedItems}"
                       ItemTemplateDataContextType="Node">
    <syncfusion:SfTreeView.ItemTemplate>
        <DataTemplate>
            <Grid>
                <CheckBox IsChecked="{Binding IsChecked, Mode=TwoWay}" 
                          FocusVisualStyle="{x:Null}"/>
                <TextBlock Text="{Binding Content.Name}" 
                           Margin="25,0,0,0" 
                           VerticalAlignment="Center"/>
            </Grid>
        </DataTemplate>
    </syncfusion:SfTreeView.ItemTemplate>
</syncfusion:SfTreeView>

<syncfusion:SfTreeView x:Name="treeView"
                       ItemsSource="{Binding Items}"
                       ChildPropertyName="Children"
                       LoadOnDemand="TreeView_LoadOnDemand"/>

private void TreeView_LoadOnDemand(object sender, LoadOnDemandEventArgs e)
{
    var node = e.Node;
    var model = node.Content as MyModel;
    
    // Load child items asynchronously
    var childItems = LoadChildItemsFromDatabase(model.Id);
    node.PopulateChildNodes(childItems);
    
    e.HasChildNodes = childItems.Count > 0;
}

<syncfusion:SfTreeView x:Name="treeView"
                       ItemsSource="{Binding Items}"
                       ChildPropertyName="Children"
                       AllowDragging="True"
                       SelectionMode="Multiple"
                       ItemDropping="TreeView_ItemDropping"/>

private void TreeView_ItemDropping(object sender, TreeViewItemDroppingEventArgs e)
{
    // Validate drop operation
    if (!IsValidDrop(e.TargetNode, e.DraggingNodes))
    {
        e.Handled = true; // Cancel drop
    }
}