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How to: Find the Index of an Element

This example shows how to find the index number of a newly added element by using the IndexOf method.

The following example defines a host DockPanel element in Extensible Application Markup Language (XAML) and uses a Button to invoke the FindIndex custom method.

<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>

The related events are handled by using code behind. The index position of the element is reported back as a text string.

		private int c_counter = 0;
		void FindIndex(object sender, RoutedEventArgs e)
		{
			c_counter+=1;
			// Create a new Text element.
			TextBlock newText = new TextBlock();
			// Add this element to the UIElementCollection of the DockPanel element.
			MainDisplayPanel.Children.Add(newText);
			// Add a text node under the Text element. This text is displayed. 
			newText.Text = "New element #" + c_counter;
			DockPanel.SetDock(newText,Dock.Top);
			// Display the Index number of the new element.    
			TxtDisplay.Text = "The Index of the new element is " +  MainDisplayPanel.Children.IndexOf(newText);
		}

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