TreeView, WPF

This control supports a hierarchy of items. We use it to contain TreeViewItem elements. We can add these TreeViewItem objects in a C# event handler.

On your TreeView control, add the "Loaded" and "SelectedItemChanged" attributes. Press tab and they will be added automatically by Visual Studio.

Example code

In TreeView_Loaded, we create 2 instances of TreeViewItem objects. For each item, we set the Header, and use a string array for the sub-items.

<Window x:Class="WpfApplication20.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <TreeView
            HorizontalAlignment="Left"
            Height="200"
            Margin="10,10,0,0"
            VerticalAlignment="Top"
            Width="300"
            Loaded="TreeView_Loaded"
            SelectedItemChanged="TreeView_SelectedItemChanged"
            Background="AliceBlue"/>
    </Grid>
</Window>
using System.Windows;
using System.Windows.Controls;

namespace WpfApplication20
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void TreeView_Loaded(object sender, RoutedEventArgs e)
        {
            // ... Create a TreeViewItem.
            TreeViewItem item = new TreeViewItem();
            item.Header = "Computer";
            item.ItemsSource = new string[] { "Monitor", "CPU", "Mouse" };

            // ... Create a second TreeViewItem.
            TreeViewItem item2 = new TreeViewItem();
            item2.Header = "Outfit";
            item2.ItemsSource = new string[] { "Pants", "Shirt", "Hat", "Socks" };

            // ... Get TreeView reference and add both items.
            var tree = sender as TreeView;
            tree.Items.Add(item);
            tree.Items.Add(item2);
        }

        private void TreeView_SelectedItemChanged(object sender,
            RoutedPropertyChangedEventArgs<object> e)
        {
            var tree = sender as TreeView;

            // ... Determine type of SelectedItem.
            if (tree.SelectedItem is TreeViewItem)
            {
                // ... Handle a TreeViewItem.
                var item = tree.SelectedItem as TreeViewItem;
                this.Title = "Selected header: " + item.Header.ToString();
            }
            else if (tree.SelectedItem is string)
            {
                // ... Handle a string.
                this.Title = "Selected: " + tree.SelectedItem.ToString();
            }
        }
    }
}

Some notes

In TreeView_SelectedItemChanged, we detect each time the user clicks on (or moves to) an item. First we cast the sender object to the TreeView type.

A TreeView supports a nested, hierarchical display of items. We use TreeViewItems to support nested items, and we detect the currently-selected element with SelectedItemChanged.