<Page xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" x:Class="WpfApplication1.IndexOfSample" WindowTitle="UIElementCollection IndexOf Sample"> <DockPanel Name="ParentElement"> <TextBlock DockPanel.Dock="Top" Name="TxtDisplay"></TextBlock> <Button DockPanel.Dock="Top" Click="FindIndex">What is the Index Number of the Element Just Added?</Button> <DockPanel Name="MainDisplayPanel"> <TextBlock DockPanel.Dock="Top">Text 1</TextBlock> <TextBlock DockPanel.Dock="Top">Text 2</TextBlock> </DockPanel> </DockPanel> </Page> //File:Window.xaml.cs namespace WpfApplication1 { using System.Windows; using System.Windows.Controls; using System.Windows.Documents; public partial class IndexOfSample { void FindIndex(object sender, RoutedEventArgs e) { TextBlock newText = new TextBlock(); MainDisplayPanel.Children.Add(newText); newText.Text = "New element # "; DockPanel.SetDock(newText,Dock.Top); TxtDisplay.Text = ""+MainDisplayPanel.Children.IndexOf(newText); } } }