using System.Data;
using System.Windows;
using WpfApplication1.db2DataSetTableAdapters;

namespace WpfApplication1
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            db2DataSet ds = new db2DataSet();
            TreeTableAdapter tree = new TreeTableAdapter();
            tree.Fill(ds.Tree);
            DataRelation rel = new DataRelation("parent_child",
                ds.Tables["Tree"].Columns["CategoryID"],
                ds.Tables["Tree"].Columns["ParentID"]);
                ds.Relations.Add(rel);
            treeView.ItemsSource = ds.Tables["Tree"].DefaultView;
        }
    }
}

<Window.Resources>
        <HierarchicalDataTemplate
            x:Key="DetailTemplate"
            ItemsSource="{Binding Path=parent_child}">
            <TextBlock Text="{Binding CategoryName}"/>
        </HierarchicalDataTemplate>
        <HierarchicalDataTemplate
            x:Key="MasterTemplate"
            ItemsSource="{Binding Path=parent_child}"
            ItemTemplate="{StaticResource DetailTemplate}">
            <TextBlock Text="{Binding CategoryName}"/>
        </HierarchicalDataTemplate>
    </Window.Resources>
    <Grid>
        <TreeView Name="treeView" 
                  ItemsSource="{Binding Tree}" 
                  ItemTemplate="{StaticResource MasterTemplate}">
        </TreeView>
    </Grid>