Define the TreeView control in XAML with a HierarchicalDataTemplate to handle the nested structure:

<TreeView x:Name="CategoryTreeView" Height="400" Width="400">
    <TreeView.ItemTemplate>
        <HierarchicalDataTemplate ItemsSource="{Binding Children}">
            <TextBlock Text="{Binding Name}" FontSize="13" Margin="3,0,0,0" VerticalAlignment="Center"/>
        </HierarchicalDataTemplate>
    </TreeView.ItemTemplate>
</TreeView>

Create the data model to represent each node, including a collection for child items and a property to link to its parent:

public class CategoryNode
{
    public int Id { get; set; }
    public string Name { get; set; }
    public int ParentId { get; set; }
    public ObservableCollection<CategoryNode> Children { get; set; }

    public CategoryNode()
    {
        Children = new ObservableCollection<CategoryNode>();
        ParentId = 0; // Root level nodes default to 0
    }
}

In the code-behind, populate the control by converting a flat list into a recursive hierarchy using a LINQ-based method:

public partial class HierarchyView : Window
{
    public HierarchyView()
    {
        InitializeComponent();
        var flatList = FetchMockCategories();
        CategoryTreeView.ItemsSource = ConstructTree(0, flatList);
    }

    private List<CategoryNode> FetchMockCategories()
    {
        return new List<CategoryNode>
        {
            new CategoryNode { Id = 1, Name = "Electronics", ParentId = 0 },
            new CategoryNode { Id = 2, Name = "Clothing", ParentId = 0 },
            new CategoryNode { Id = 3, Name = "Laptops", ParentId = 1 },
            new CategoryNode { Id = 4, Name = "Smartphones", ParentId = 1 },
            new CategoryNode { Id = 5, Name = "Gaming Laptops", ParentId = 3 },
            new CategoryNode { Id = 6, Name = "Ultrabooks", ParentId = 3 },
            new CategoryNode { Id = 7, Name = "Android", ParentId = 4 },
            new CategoryNode { Id = 8, Name = "iOS", ParentId = 4 },
            new CategoryNode { Id = 9, Name = "Men's Wear", ParentId = 2 },
            new CategoryNode { Id = 10, Name = "Women's Wear", ParentId = 2 }
        };
    }

    private List<CategoryNode> ConstructTree(int parentId, List<CategoryNode> sourceNodes)
    {
        var rootNodes = sourceNodes.Where(n => n.ParentId == parentId).ToList();
        var remainingNodes = sourceNodes.Where(n => n.ParentId != parentId).ToList();

        foreach (var node in rootNodes)
        {
            node.Children = new ObservableCollection<CategoryNode>(ConstructTree(node.Id, remainingNodes));
        }

        return rootNodes;
    }
}